Why am I not getting three and four stars stickers. I'm only getting one..

Ok can

Love how monopoly go devs haven't even touched on this... My guess?? Because the game wants you to have to pay to complete the events that give the high-star sticker packs. Don't know for sure, but that's my best guess. They reserve all high-value wins for their pay-to-play & pay-to-win players. But as I said, this is anecdotal. In my experience this is true and how it has worked for me, but there could be different algorithms for different players, not sure.

Me to don't get 4 or 5 star cards

Not pay only. I have never spent anything and I am 2 golds from completing the entire set. Should be able to get one more new card on a 700 star vault and hopefully trade other on gold event or maybe just be awarded them. Just so all knows. Spending not required. I am a bit obsessive and stay on top of trading when I can and even trading up to 6 cards at once for one I need. Some are always looking for just the volume of stars. I do spend way to much time on it all but oh well. Phase 10 was getting redundant. Lol.