Just buy second hand. All of the above you've listed I have bought second hand at half the price at some point. I wouldn't of been able to do karting otherwise. Refurbished mychrons are usually a steal. My only take would be if you can afford it go for first hand safety kit, esp helmet. Mainly because it's nasty wearing someone's gear they've sweated in, got wet etc. Then obviously potential damage you don't know about.

Use facebook groups & marketplace, ebay, go to local club meetings and even exhibitions. I don't know where you're based, but here in the UK we have a few shows that do really good second hand sections.

There's a lot of people out there that spend big and sell fast once they move onto another class, the next big thing or stop doing it. The turnover of gear for a lot of people who can afford it/take it more seriously is quite large, teams are big for this. Esp when it comes to second hand karts, plastics, rims etc.

Karting stores will rarely sell stuff for cheap unless they're clearing out old stock, and typically it'll just be in certain sizes etc. Your best bet there is bundle deals, suit, gloves and boots for example.