You need to consider what you will be doing with the bike to determine which mods will suit you best.
Reeds, Pipe, Jetting, reed spacer, and muffler packing, are fairly quick and easy.
Most of the rest of the mods start requiring increasing amounts of time and money.
Besides installing all new bearings and seals, a new top end is always welcome as well as Larry's Decompression and head squish mods.
Cleaning up your bridges, transfers, and ports is a welcome addition as well.
Balancing your crank is also a must.
But, it all costs money and time.
I don't know where it originated but on Mad Max there was a sign at a wrecking yard that read "Speed is just a question of money... how fast can you go?"