It's hard to find a game without IAP (in app purchases) these days and that's a shame as Pay 2 Win really isn't about skill, it's just how much you can sink in. That said, developers often need to incentive to keep developing a game and to pay for the costs such as servers, etc. I remember there were a few games that were Pay to Play on the horizon, but after their announcement, they never seemed to materialise. Anyway, I'm waffling. Basically I'm okay with an upfront cost or a subscription, I just want a good game which appears to have longevity and as few events as possible. I want to play when I want to play as opposed to when the developers want me play.
Old School RuneScape is a good pick. Great game and solid mobile client.
If you're okay with optional cosmetic mtx then Albion might be worth looking at too.
AdventureQuest 3D has a single class exclusively behind paywall, but it's a one-time fee. Beyond that it's cosmetics and crafting speed-ups for real money currency (which is also earnable from normal gameplay)
Since the game is getting a rather big addition in a few days: RuneScape 3 is also not bad, but if you want to avoid mtx and p2w you have to pick the "Iron(wo)man" option when you start. This removes the ability to trade or use the auction house system, but in return all the p2w is stripped out (and imho the progression of your character becomes much better)