Koolstop salmon break pads and supple tires with correct tread.

Proper clothing such as mountain bike short liners, or full on road bike/ MTN bike kit. Pedals and shoes to match. Personally I went with DC skateboard shoes and flats with pins not bolts. Bolts will tear up your shoe bottoms. Make sure your handle bar is the correct width and has the correct stem length.(bike fit) No need to get expensive light weight versions. Just the correct size to fit you. Seat/saddle can make a large change in the comfort of the bike. These can all be used on a different frame if you upgrade bikes in the future.

Can you work on the bike yourself? Then a cheap bike stand, tools, and a tube of grease(espicaly if you have cup and cone hubs). Are you missing shifts on the rear cassette? Was able to fit a shimano deore long cage rd-m592 rear derailleur on my hybrid to replace atlas rear derailleur(use a new chain at the same time). Do not know what to tell you about shifters. Ones that I like are no longer being made. Just please remember fixing, working on, replacing parts will not move this bike out of its class and price range. Just will move it to the top of the class and price range. Many things will not be cost effective or even possible.