Nah! Ignore the naysayers! I'm ruddy cheap as chips too! Hell, I'll try and fix anything at least once before resorting to buying a replacement. There are very few things that can't be repaired or recreated on the older SS games. DMD and modern games tend to have a lot of moulded scenery that can be really hard to find and almost impossible to repair, but SS games are generally flat single-level and re-use far more parts from across a series of games.
In fact, I've not bought many new parts at all. Obvious purchases are "consumables", i.e., balls, coil sleeves (and I got ribbed for cleaning some old ones that were still tip-top), rubbers and lamps. I did by some new parts for the linear-style flippers in VECTOR, but decided not to get a full "rebuild kit" as they were £55 a pair and VECTOR has 4 flippers! I simply improved things by doing a full stripdown of the flippers and meticulously cleaning and polishing each component.
There are a bunch of handy tools, mostly inch size for US parts, and stuff like wax for polishing and cleaners, but you might have adjustable spanners and, according to at least one member on here, Pledge is the best polish for pinballs
Because I'm happy to fix the electronics I've bought a lot of electronic components too but if you hunt around you can get good prices on everything and things like capacitors, resistors and diodes are just few pence each. I recently found some new-old-stock Motorola 6800 microprocessors for 32p each, they're usually around £5-10 (they're obsolete and haven't been made for years).