I have a Force/Tech lvl 63 Character and I look for a unit sett, I found that the ray sett is one of the best for my class, but it requirements of dex are to high for me, I have to level up to 75 in order to use it, or there's another way?

It is just a matter of leveling. If you are Human, Deuman, or CAST, you should be able to equip them by lv75/75 Fo/Te, but if you are a Newman, you need to wait until lv76.

Since the cap is now lv80, you don't need to worry too much about getting extra DEX outside of normal leveling, but you should be aware that if you get Bouncer and Braver to level 75, you will get an extra 60 DEX added to your base stats on all characters.