Speaking from experience:
250k will most certainly be not enough if you want to run your own turnkey. 500k will be extremely difficult unless you run with a very lean team, shitty support, risk and compliance and a shitty software stack. With around 1m things will be comfortable enough to operate 12-18 months before you hit any profit.
The biggest issue are these things:
1) You most likely will overpay for many things and get shitty deals for your license, company structure, software provider. Often things will look good until you paid, and realize a) the service isn't as good as advertised and b) the software provider has a lot of limitations in terms of functionality or lack of integration for payments etc.
2) You need to budget for things you don't even know you need yet. Initially you think you only need a company and the license ~30k. Then you might want to pay another UBO to be on the company. Then you realize you need a payment company to get payments in certain locations for 5k. Then you need a bank account for that company for 2-3k. Cool, now your'e up and running.
Now you get a software provider, but the activation +minimums are crazy high 10-30k + 5k a month after.. You will pay even if you dont have traffic after 6 months. Want sportsbook? Oh thats another 5k+ after 3-6 months. Now you want to get affiliates onboarded, oh you need to use a third party for 2k a month. Want to do CRM? Sure, heres another 5k a month.
Now this are just costs for part of the tech. Want to get payments? Sorry we dont integrate custom pyaments, you need to use a cashier like payment IQ. Another 5k a month.
Now your monthly bills are already 20-30k a month, WITHOUT a team and without acquisition. Now you need to hire staff. You need support 24/7 to cover multiple shifts. Then you need them to handle payments 24/7. You need to hire someone who understand risk/fraud to flag bonus and payment abuse. You need to do KYC. You need people to answer tickets.
If you want payments, you need to be technical enough to do it yourself or hire a specializt to do the integrations with the cashiers (if youre lucky the provider has it already).
Now you need a CRM person who does all the promotions, a casino manager who roatets the lobby and games. You need to either a) run traffic yourself, b) find affiliates and be the affiliate manager or hire one c) hire an agency and manage them (or all 3 of them).
Now you don;t even know your LTV. When is your payback? You might do things for 3-6 months, not knowing how much you can afford per CPA. Affiliates and streamers try to scam you. You will make a lot of mistakes costing you tens of thousands just to learn.
Overall everything is just extremely expensive, a lot of companies understand that selling the shovels is more lucrative than actually digging the gold.
My advice to my younger self would be:
Start with a cheap white label solution that has a lot of payments/functionalities. Play and test the platform that are live. See what they're doing, gauge how much traffic they get.
Yes, they will steal your data and cross sell your VIPs to their own brands. but at least your risk will be 50-100k until you see if this business is for you, and most importantly if you can generate acquisition thats profitable. Starting with a stacks thats ready to accept players will save you so much already, because what I describe with the above with payments and all integrations you will lose at least 3-6 months just waiting for things to be ready, WHILE paying for all the ongoing cost. The fail rate of startups is extremely high, as this is an ultra competitive landscape and you compete with a lot of big boys who can outspend you.