Welcome!
You should start by clicking on the link in my signature for New Members. (need landscape mode on mobile)
Then you've given us some good info, but lets explain what you're asking.
You have chips, but you are using them wrong, you said with the denoms, but you didn't say if you've declared them or if they are actually labeled as such.
Efficiencies would have a chip value and then the next denom x 4 or x 5 of the previous denom. So it could be you can reuse your chips, just declare them a different value.
.25 is a good start, but you can't have both .25 and .5 with only 500 chips and you shouldn't spread them both anyway.
To start with a chip break down you should first figure out how much USD or EUR you need to support in chips. It sounds like a cash game to me.
50 as the buy-in x 8, so thats the bank to start, but lets say everyone is going to buy in 2 times (buy-in plus 1 rebuy), you're looking at 50 x (8 x 2).
800 is your bank, but I like to add 10% and round up to the nearest 100, so 880 > 900 USD?
.25/.5
I would do something like:
100 x .25
160 x 1
200 x 5
40 x 20 (or 25)
