This game is a very easy 800G, However it will take patience and time to get gold on every mission. 

I would suggest playing the game through first single player on easy, and then online on hard with a friend, collecting all of the posters and targets for 1 person, so that one person can get all of the gold medals. I do not think its possible for both people to get gold on all missions.

On the first playthrough on EASY you should get around 660G. This is if you buy everything (use the glitch) and collect 5 posters on one level and 5 targets for one level. Then you will get around 145G more for playing through the game as a member of G-Unit. 

ACHIEVEMENT GUIDE

I'm Supposed To Die Tonight - 20 points

Complete Mission 1 on any difficulty

See “Bulletproof” achievement below.

Get In My Car - 20 points

Complete Mission 2 on any difficulty

See “Bulletproof” achievement below.

Candy Shop - 20 points

Complete Mission 3 on any difficulty

See “Bulletproof” achievement below.

Straight To The Bank - 20 points

Complete Mission 4 on any difficulty

See “Bulletproof” achievement below.

Disco Inferno - 20 points

Complete Mission 5 on any difficulty

See “Bulletproof” achievement below.

Amusement Park - 20 points

Complete Mission 6 on any difficulty

See “Bulletproof” achievement below.

Gunz Come Out - 20 points

Complete Mission 7 on any difficulty

See “Bulletproof” achievement below.

I'll Still Kill - 20 points

Complete Mission 8 on any difficulty

See “Bulletproof” achievement below.

Gotta Make It To Heaven - 20 points

Complete Mission 9 on any difficulty

See “Bulletproof” achievement below.

Got Paid - 25 points

Complete all missions on Easy or better difficulty level

See “Bulletproof” achievement below.

Gangsta - 50 points

Complete all missions on Normal or better difficulty level

See “Bulletproof” achievement below.

Bulletproof - 100 points

Complete all missions on Hard difficulty level

This game is not that hard and only heats up around the 6 -7th mission. However from there on it can be quite infuriating. Because of the long checkpoints and the annoying turrets, molotovs and bazookas this can be quite a frustrating game for some. Take it slow and do the money glitch so that you can have the best weapons early on. Do not worry about getting gold on all of these levels as you can select the missions you didn’t get gold on from the main menu. 

Packin' Heat - 10 points

Unlock all pistols

See “Tooled Up” achievement below.

Point Blank - 10 points

Unlock all close combat weapons

See “Tooled Up” achievement below.

Rifled - 10 points

Unlock all assault weapons

See “Tooled Up” achievement below.

Explosive - 10 points

Unlock all special weapons

See “Tooled Up” achievement below.

Tooled Up - 50 points

Unlock all weapons

Do the money glitch mentioned at the bottom of the guide. It will cost just under 100 000 000 to obtain ALL weapons and about 200 000 for everything else.

Wanna-be - 10 points

Obtain 15 or more Silver Badges

See “O.G” achievement below.

Regular - 25 points

Obtain all Silver Badges

See “O.G” achievement below.

Hardcore - 50 points

Obtain 15 or more Gold Badges

See “O.G” achievement below.

O.G. - 100 points

Obtain all Gold Badges

You should do this on co-op on hard. Collect all of the posters and targets and don’t die. Chain combos and ALWAYS press the left stick after every kill for a taunt that gives you 25% more points. This is by far the hardest achievement in the game. Watch these videos for locations of all of the collectables and walkthroughs for gold medals on hard. 

HERE ARE ALL THE WALKTHROUGHS 

Thanks a bunch to Swaggers for them.

Savior - 5 points

Revive a co-op player

This must be done online. Easily done on any difficulty.

We're Supposed To Die Tonight - 10 points

Complete Mission 1 on any difficulty as a member of G-Unit

See “G-Unit” achievement below.

Get In Our Car - 10 points

Complete Mission 2 on any difficulty as a member of G-Unit

See “G-Unit” achievement below.

Our Candy Shop - 10 points

Complete Mission 3 on any difficulty as a member of G-Unit

See “G-Unit” achievement below.

We're Going Straight To The Bank - 10 points

Complete Mission 4 on any difficulty as a member of G-Unit

See “G-Unit” achievement below.

Our Disco Inferno - 10 points

Complete Mission 5 on any difficulty as a member of G-Unit

See “G-Unit” achievement below.

Our Amusement Park - 10 points

Complete Mission 6 on any difficulty as a member of G-Unit

See “G-Unit” achievement below.

Our Gunz Come Out - 10 points

Complete Mission 7 on any difficulty as a member of G-Unit

See “G-Unit” achievement below.

We'll Still Kill - 10 points

Complete Mission 8 on any difficulty as a member of G-Unit

See “G-Unit” achievement below.

We Gotta Make It To Heaven - 10 points

Complete Mission 9 on any difficulty as a member of G-Unit

See “G-Unit” achievement below.

G-Unit - 50 points

Complete all missions on any difficulty as a member of G-Unit

Just join someone’s online game and race through it on easy. It should only take 4-5 hours on easy. Or link this as stated above with the medal achievements.

Hit and Run - 10 points

Run over a foot soldier in a driving section

This is nearly unmissable, as in its dead easy and will probably happen whether you're trying or not. 

Ramping Up - 10 points

Complete any of the ramp scenarios in a driving section

Just hit any ramp in mission 2.

Death From Above - 10 points

Destroy 50 vehicles and destroyable objects on the flying level without dying

I would suggest doing this achievement on easy as it is a hard level on hard and you probably will die before you get it. This should be done on single player, so as the other person doesn't destroy the objects before you.

Up Close - 5 points

Perform a counter kill

This will happen in the first 2 minutes of the game.

Got It Done - 5 points

Successfully complete one scenario

Unmissable.

Scenario Master - 20 points

Successfully complete 50 scenarios

Just do some of the quick scenarios that pop up on screen, these are the things with the time limits. Most of them you will do by accident and I got this achievement halfway through mission 3.

Black Belt - 40 points

Unlock all counter kill packs

These cost around 200 000. There are 8 different packs. See the glitch below.

Sharpshooter - 25 points

Kill an enemy by shooting a rocket or grenade out of the air using Gangsta Fire

This achievement is not that hard and I did it on my first playthrough. You can do it at many points throughout the game, so just keep trying. Just find a rocket man who shoots a rocket near to another enemy. Then after he has shot enter Gangsta Fire and shoot it. If you miss then just try again or reload the checkpoint.

Fly Poster - 15 points

Collect all 5 posters on any level. This can also be achieved by assisting another player in Co-op

See any of the video walkthroughs above under the “O.G.” achievement.

Target Practice - 15 points

Shoot all 5 targets on any level. This can also be achieved by assisting another player in Co-op

Flying High - 10 points

Score air time from a single character for more than 10 seconds

This will probably happen on its own, during the course of a playthrough.

Massacre - 10 points

Kill 5 enemies fast enough to score a 5 kill combo

This will definitely come through the game, if you’re having troubles then do this on a turret part of the game and it will be easy, or on the flying level.

Millionaire - 50 points

Have 1,000,000 dollars in the bank

For this achievement you must have 100 000 000 in the bank at one time, but do not fear. There is a money glitch for this game and with this method it will take roughly 20 mins to get 1000 000 000.

I would suggest getting around 100 200 000 that way you can buy everything and get all of the achievements that require money all at once. It should take around 25-30 mins to glitch this amount of money. See the video below.

Credit geos to xCheezbrgr for the video.