I am just finishing up with a lot of printing and going to pull the Prusa MK3 apart and repack the bearings. I got it a little over a year ago and have done a good amount of printing. I have already done B7 upgrade for the fan and OctoPrint with Raspberry 3. Other than that I have done nothing. i had used printed linear bushing for about 6 months but they started to bind and I put back the originals.
There are a boat load of upgrades and suggested upgrades and upgrade lists. My head is starting to spin.
I am going to do the Energy Chain upgrade that I found on Thingaverse.
Go ahead and make your must do and would be nice upgrades.