So Im at Orphen's Cradle. And I've been doing a bunch of missions trying to level up. For the most part it's been successful and I have the Growth Egg. I want to get Omega weapon but I need the Trapzeohedron which costs a good 2Mil. Is there a good way or place to farm Gil so I can get it and how long will it take? Or do I have to wait until Post-Game to get it?

Go back to Pulse and give those Adamantoise a few beatings.  It will help if you have a Connoisseur Catalog equiped to increase the ridiculously low drop rate.

But yes, it will help if you do all that post-game, since you will have unlocked the last Crystarium level and have stronger characters.

adamantoise drops them sometimes ( big or ssmall one)

Whats the point of having a post-game if there is no new game plus? In all honesty it just sounds frickin retarded.

after you beat the last boss u get the last crysalluim lv up whcih you will need to beat the last of pulse hunts

The best place to get that is to farm the Admantoise in Eden. its not that hard, and even though it takes ages to get 1, you'll be glad because you should have a lot of platinum ingots by then.

theres 2 ways to go from there, but make sure you have a collectors catalogue. the reason is because even when you get 1 Trap, the cost to get ultracompact reactors is staggering, and you need these to level the weapons up. so you can either use the money to power up more weapons or buy Traps, (dont buy em). i got 7 Trap drops  by the time i finished and i still didnt have enough ingots to get 1 of each weapon (and just 1 of everyones ultimate weapon) powered to their max levels.

imo, the system is flawed because theres some weapons you'll never use, and the only reason you do this quest is for the trophy, and theres no way to make money fast like in other FFs to power up the weapons straight away.