I’ve not used them off-road but on the road bike I’ve just fitted a full set of KCNC cables, they’re ace and didn’t need any oil/grease. Those and SP41 by the meter is cheep so probably £10-£12 for the lot. And a bottle of ‘cable magic’ lube for another fiver.
Spend the rest on somethign out of the folowing.
Tubeless if you’re not already, getto costs about £20 inc a bottle of stans.
Tyres – although £50 doesnt go very far these days
Suspension service kit.
Foam grips – biggest weight saving (thnik some are silly at 18g Vs upto 200g for lock ons) and lots of comfort and (IMO) more grip than rubber grips.