Mostly a reader, rarely post, so here is my short checklist for choosing a casino site. After a few bad experiences I stopped going by ads alone.
Licence comes first for me: find the licence number and look it up, and whether they actually accept players from your country. After that I look at banking: card, e-wallets and bank transfer should all be there, and there should be no weird fees on cashouts.
The welcome offer is where most people get caught. Anything above 40x rollover is a red flag for me, and some games count less towards it. A good recent review that covers all of this is here bonus at Rolletto and it saved me some time.
On mobile I mostly use the browser version, and a good site loads fast and does not log you out every five minutes. Test the live chat before depositing: if they answer in a couple of minutes that is a good sign.
That is about it. Only play with money you can afford to lose.