Just forget that mobile gaming exists? I think one of the cheapo Linux retro handhelds offer a better portable gaming experience than 99% of mobile games, ads or no.
I rather like the Anbernic RG35XXSP for the form factor. It is missing analog sticks, which does cut down on playable games a little but it's cute and tiny and is decently powerful for the price and has good community support. The rest of the RGYYXX line(where YY is the screen size) uses the same hardware but have different form factors so you can pick what you like best.