This whole point of using altcoins as a possible collateral seems to be strained at best and far-fetched at worst with forced arguments at that. It is not enough that you as a borrower might think that the altcoin in question would grow in price, you should also convince the lender in that. If you somehow succeed, the lender would be willingly and wittingly selling you bitcoins for that altcoin and then buying them back at a loss. Why would he want that?
What? No, not selling. That is collateral. Which is usually held in escrow.
The borrower shows proofs to the lender that he has the altcoins
The lender checks the current value of said coins
They agree on terms
The control of the coins is transferred to the escrow and
The loaned amount is released to the borrower
When the loan is paid by the borrower, the escrow releases the altcoin back to the borrower.
If however, the loan is not repaid, then the escrow releases the altcoins to the lender.
@OP sorry if we are getting off-topic.
Now, my suggestion for casino bankrolls. I would go for casino sites that do not have too big of a bankroll yet.
Going for moderate bankrolls could possibly give one bigger chunks of the profits as there would be fewer investors to divide it among. (Especially when compared to sites with huge bankrolls and thousands of investors.)