i have problems with the whole upgrading/buying system, i guess i'm just not sure if i should do it at all.

please note, that my plan is to simply finish the game. i am not planning to get ever trophy, or kill every optional boss (if there are any). and no spoilers please (i'm roughly in the middle of the game).

my problems is that i started to level up my starting weapons, and now they are around level 8, so they give like 50strength/50magic, and all the weapons i can buy/find are like 10strength/10magic. why should i buy them?

those new weapons i can buy or find do offer some additional benefits, like bonuses for debuffs and such, but the primary attributes are very low at level1, so i would have to upgrade them to the level of my current weapons.... but then i could also just continue upgrading my current ones.

Some of the weapons that start off as total garbage can end up being very powerful if you upgrade them. And in some cases yes weapons do have special effects.

Basically weapons exist for the purpose of the passive bonus. With a few exceptions (such as that weird magic cape for Snow) weapons have fairly similar stats so you should grab one with a bonus you like and upgrade it.