Here are some cheats/tips I want to share with you that might be useful:
Finding stairs quicker:
As you know some pokemon become petrified and run away when you have hit enough on them, but dont kill them or let them run away, follow them! If you follow them they should show you to the stairs to the next floor, and this works for me most of the time.
Easier way to get up floors on Wish Cave:
If you want to get up floors and keep alive on wish cave, here is what I recommend: Take Huge Apples, an escape orb, reviver seeds, max elixirs if you want, and wear a pass scarf or x-ray specs or have a warp scarf.
Reason for pass scarf: Most moves used on you will just not hit you and backfire to a pokemon around you, giving you the chance to stay alive better. (Do not let a pokemon on your team the move will backfire on them)Its also good for thieving Kecleon Shops, as ALL of their moves will backfire on them.
Reason for X-ray Specs: This will enable you to see your enemies an items, so you can easily dodge your enemies, unless you walk into a dead end or they come from the all ways, then you'd need pass scarf.
Reason for Warp Scarf: This will allow you to warp to random places on the same floor, so if it warps you near the stairs take it of, go to the next floor an put it on again unless the stairs are near you.
Easy beating legandaries:
If you want to beat legendaries easily, the move I recommend is Bullet Seed. I started using that from Groudon on, and now I'm hitting in my 400 to like 1500 with just 1 hit. Also dig is good so you can hide for a turn so the legendary cannot attack you. Quick attack is a little bit useful because of the 2 tile ranged aswell but it is not as good as Bullet Seed and dig. Also try to confuse them (seeds or moves) paralyze (seeds or moves) or put them to sleep (seeds or moves)
I will try to add some more useful tips, but try and use these ones for now :)