If your looking for a project great, but it will be cheaper to just buy a newer one.
Your BEST UPGRADEs are tank, loader, and paint. just remember that. They work will all markers not just spyders. The VL jr. will serve you fine.
Then barrel, feedneck. Old spyders have rather crappy barrel, but the new ones are just fine. start looking, but any 1-piece barrel will be better than stock and you probably don't need a full kit. CCM makes good quality feedneck, then there's idk trinity makes budget feed necks. I actually for my e-99 use an ion thread adapter so i can use many different feednecks. ( tabed with holes is e99)
Free mods!- look em up, can be useful if you have the skill/tools.
anything more you will need to pick up a regulator and spring kit to start. I suggest using the search function to help you start.