I can tell you from experience that its a dog eat dog industry.
I was early in 2013/14 but I would not join nowadays.
You could contact "SoftSwiss". They are the leading Crypto-Casino supplier. White Label solutions, Turnkey and also Betting-books.
If you want go to the poker area, microgamings.co.uk is also a good option to have contact with.
BUT AGAIN:
It is very expensive. The price for developers, royalties for games, gambling licenses in Malta/Isle of Man/Costa Rica.....
Look into it, but you will need at least 1 million $ for advertisement alone.
Its not enough to buy the software for 25-100k$
I would not plan with buying software - what does it cost to built a own software? What people would need this?
It all depends on what you want to do. My personal experience tells me, you NEED a normal Casino floor, slot games, sport betting and then poker rooms.
If you look around, other casinos got well over 600 games. No-one can play them all, but its industry standard. If you don't got that, you are not taken serious by customer for some reason. Big is not always better but standard in the case.
If you really want to go from scratch plan a bit like this:
All in USD
40-60k for a running backend with wallets (i assume multiwaljlets is best)
10-20k for the frontend
min. 2k per game maybe more
And again, at least 1 million for advertisement.
Cost of Staff:
Then there are cost of staff. You will need a good casino manager. Experts are rare and really good experts that are in the industry since the 90' cost easily 100k/year plus Boni.
Other Costs:
Rake of at least 20% is standard in the casino world.
Boni for deposits and Special Rewards for trusted players are on ave over 30% (Deposit Bonis can go 300%)
Affiliate costs
Programer royalties of around 10-20% (even if you don't buy software and let it build from ground, programers take royalties for every $ earned with their game)
This is just an overview. I have spend a long time in this industry. You can now believe me or call me crazy. But this is what you need to calculate :/
And also please consider, that its not just crypto casinos you are competing with. The big boys of the fiat world are transitioning into crypto as well. And they are in the business for more than 20 years.... They can always pay more for marketing and service than a single or small group is able to.