Putting magic in stats is called 'Junctioning' and increases stats. For example, in the beginning of the game, Water is a good spell to Junction on Strength.
That is to say, your magic is more fucking useful for that then to cast it. But there are two spells worth casting the whole game. Aura, which makes you be able to use the Limit Breaks which usually don't come until your health is yellow (critical), and Meltdown, which makes every monster, including every boss in the game, even the final boss and the optional bosses, have 0 defence.
Weapons aren't bought until you have certain amount of certain items that certain enemies drop at certain levels (depending on the level of the monsters, they drop different items). Every monster and boss, even the final boss and optional bosses, level up with you. If you are lvl 30, all enemies are lv 30. Actually, there are three exceptions to that rule.
At the beginning of the game, you have to go to a cave that is filled with fixed lvl 5 enemies. There are two islands that have fixed lvlv 100 enemies. And on the PS1, Omega (an optional boss) is at a fixed lvl 100.
Are you beginning to understand why FF8 is stupid!?