Eggplant

really depends on your standards. and desired genre.

i can do basically orchestra, rock, or chiptunes.

haven't the slightest clue about electronic etc.

for orchestra, it's always possible to arrange a draft via midi (like the one i linked) and then ask real instrumentalists to record some parts for me, which would drastically improve sound quality.

or i can buy / learn to use better samples.

How much do better samples cost, lets pretend I know nothing about the specific details on that kind of stuff, instead of knowing that I don't.

no clue dude. depends how much i want to upgrade.

i haven't done tons of research on it.

probably, everything is fine as-is, bar only brass and violins.

like drums, bass, piano, ambient strings, woodwinds etc all sound realistic enough.

if i'm lucky i can just find samples for those two and plug them into my current software.

if i'm not lucky, i might need new software. or even a keyboard.

...but usually probably between $50 and $200 for new samples.