You get glide when you get lv. 3 on your final form. Once you get to lv. 3, every other level becomes a faster glide, and eventually at lv. 7 it is the highest.
Otherwise, same as what Myth. Omega said except
For Sephiroth, use Guard. It really helps. If you use my strategy, you need berserk charge and trinity limit, so just keep attacking, guard when he (with the six hit combo), then trinity then berserk charge, then repeat. Hit him before he uses the sin harvest-like move.
As for Secret ending, I almost have it. I'm 99% done and only need the last of the synthesis materials. Otherwise all it takes is that right strategies and the right information to get 100%
Ultima weapon, same as Myth. O. and don't forget to get all the Orch. +. You can find there locations on the web and stuff.