With a brand new casino, most of the chips should still be in pretty good condition. Chips are easy to take out of most casinos, you can either get them from the cashier or tables and just pop them in your pocket.
If you're looking to get higher quantities just bring a backpack in with you. Put some "poker accessories" in it, I usually have an iPad and some headphones in mine. You can get racks of $1s at the poker cage in most casinos, they just assume they're being used for $3/$6 limit or another similar game that primarily uses $1 chips. Same with $2 chips when applicable.
You can also ask the cage for uncirculated (brand new/never in play) chips, and generally people have better results when they include a tip on top of the value of the chip.
Aside from quarters/fractionals I haven't had any resistance taking chips out of a casino. It's harder to get uncirculated chips, but that depends on the casino and cashier.
Happy harvesting!