Looks like the F300 was a 2006 model, so newer than you think 😉
I’d spend your money on a good set of 2nd hand suspension forks and a new stem for starters. The like of v-brakes and grip shifter should be pretty cheap to pick up 2nd hand, as they don’t tend to be the parts most ppl are looking for (I’d suggest staying V-braked until you got the forks sorted then maybe look into some disc’s later).
You may well be able to replace all there part within your budget if you take you time and buy wisely.
Forks wise I’d suggest looking for some Rockshox Reba’s (or recons) with around 100mm travel, as this is what the frame will be optimised to work with & be reasonable weight wise. Longer travel might work too but will start to affect the way the bike was made to work, though reba/recons from a few years back can be pushed up to 120mm if you need more travel later.
Get some wanted ads going in the wtd-classifieds.
Be-aware that C’dale do have a different headset size, but as a ‘budget’ bike I reckon yours will have come with a std fork/steerer (1 1/8th), though your bars will probably be 25.4 not the newer 31.8 standard, so make sure you get this ‘older’ stem size (again tend to be less popular now, so can come up as bargains). Look for max of 100mm or shorter, but they might be harder to locate as the newer 31.8 stem sizes become the norm with shorter reach, measure the old one (centre of the steerer to the centre of the bars) & work ‘back’ from there.
Good luck.