Nice choice might be mew - it levels up fast and gain lots of hp when levelled up.
My succesfull strategy was taking:
-Some Reviver Seeds (more=better)
-3 TMs Frustration - Learn them from the start
-Some Max Elixirs
-Tm Attract for battling Jirachi or for difficult situations
-Link Box (unnecessary, because you can find a lot of them in the dungeon) - use when pokes on your floor have more than 45 hps )
-Pass Scarf to hold
-Joy Seeds - no need for explaining, but I actually clear the dungeon without them
- 1-2 Warp Orb, Slumber Orb, Invisitify Orb, Totter Orb etc. - They will help you with monster houses
- 1-2 Huge Apples - If you don't feel lucky with items in the dungeon
-Gravelerocks
I hope it'll help