Unfortunately the whole point of this part of the game is that you HAVE to give up two different things.
As you found out, the First Ascent forces you to relinquish one thing (be it Weapons, Magic, Summons, or er items i think is it?).
The Second Ascent then forces you to relinquish one of the final three things.
As a kind of rule, it really depends on how strong you are. If you're easily defeating enemies with normal Weapon Attacks (which you should be able to do by now if you've leveled up enough) then under no circumstances should you get rid of Weapons. That leaves Magic, Espers, and Items I think (if I'm wrong then someone will correct me).
If you can do without them, a good thing is possibly to get rid of Items, but it depends really. If you don't manage to charge your magic without getting killed over and over, it may be better geting rid of that and keeping Items.
Either way, you must get rid of TWO things.
Don't worry. Once you get past the Second Ascent, i think it is, you get both things you gave up back. You just have to touch the corresponding Altar to get them back.
I hope that helps.
Jay