Still shopping around...

Hey everyone! I very new to this forum and I am actually still shopping around for a 2016 Tacoma 2W TRD Sport Double Cab Short Bed and I've just been drooling over all these awesome trucks all over this site. I hope that once I buy my truck (probably by the end of this month) I will be able to make a few upgrades right away. I was curious to know what a few of the first upgrades that you would make if lets say your budget was $3,000 for just upgrades right after purchasing it? I've been watching a lot of videos and reading on here that there are certain upgrades that should be made together. This might be a stupid question but what do you do with the old parts? Let's say I were to buy new wheels and tires... do I just post them on craigslist or would the place that I'm buying my new tires from maybe buy them from me? Sorry, I'm totally new to this and before shopping around for this truck I had always driven used cars that I did not care to upgrade anything on. Thanks for any help that you guys can provide me with!