With that in mind, if you have little capital, don't open a casino. This is a business principle. If you have weak finances, it's very difficult to survive because your money will be used up by marketing and other operations. It's very rare for a small casino to become very large without substantial capital to start and attracting a large number of customers by hiring marketers, whether influencers or other similar companies.
I agree with you that casino operations requires large capital to start up since everything that relates to running a casino in capital intensive, since unlike other businesses that need low marketing to draw audience, running a casino marketing is not like that, since as a new platform, one will need to carry out aggressive marketing in order to build a space for themselves in the market and there is high competitions which make revenue generation very important to sustain a strong consistent presence.
Marketing is one of the keys but what matters most is provably fair games, transparency, trustworthiness then active costumer support, quick deposit and withdrawal now, with all these it would attract more people and also gives room or space for effective marketing.
When gamblers sees all these are something very free from the casino marketing won't be a problem the casino itself would carry out the marketing of a thing, meaning those people who are gambling on the site are same people who would keep referring their friends to come make use of that gamble site.
Now, with little efforts of marketing they will become successful, and yes funds is need normal for pay out since most people could win above the casino back balance then they must source for additional funds to make payout to the gamblers. Now, this now draws to how some casinos limits stake amount, winning amount or maximum odds to be allowed to stake on their gambling site in order for them still remain in control of their payout instead of them to go bankruptcy.