Trying to get through all the rounds of LC fight club can be frustrating but I found a solution that makes it much easier. After every round win you recover some but not all health back but if you choose to spectate in between rounds you will get all your health back and not loose progress, this comes in very handy as the later rounds people will spawn with weapons. You can also potentially get the FINISH HIM achievement (10 counters in 4min) also when trying to get this one.

Getting Half Million in TBoGT is not very hard at all from the start missions will be granting you thousands of dollars on top of that you should be doing the Drug Wars for the achievement related to those side quests and those also grant you thousands of dollars for completing relatively easy tasks. Once you have a decent amount of money Id say 50k isnt a bad starting place go to LC fight club and spectate so you can bet on the fights. There is no limit to how much you can bet as long as you got the funds. So just pick a fighter and bet all your money on him then rinse and repeat. I made an extra save just in case it auto saved over my only save if I lost all my money. I got the achievement in 2 tries not having to reload the save. Started with 87k won the first match and walked away with over 300k went and saved the game and came back and bet the 300k+ on another fight and walked away with around 850k.