That's a tough one, since I seemed to get most everything right first try [1]. Still, there are a few tweaks I could have made.

What went right:

- Hopping jobs early. I managed to roughly quadruple my salary over the first few years as a developer by switching between companies in a hot job market (though nowhere near as hot as the one today). A couple of those were "perfect company" type jobs where I could have comfortably stayed my whole career and had fun. But my value was rising quicker than they could match, so I had to move on. That seemed mean at the time, but was absolutely the right thing to do.

- Moving to contracting. Cause they pay you twice as much per hour and you can easily move on when the contract ends.

- Negotiating. I figured out early on that a good developer is worth more to a company than a company is worth to a good developer. Over time, I got more and more confident at insisting on being paid accordingly. Was constantly and consistently amazed that companies would agree to pay pretty much any number I could say with a straight face. Thought up some bigger numbers and practiced saying them.

- Living cheap and light. So that it's easy to sock away lots of personal runway and not have to worry so much about the consequences of not having a job for, say, an entire year at a stretch.

- Traveling between contracts. For like a year at a time, on account of all that extra money that contracting pays you. Reaping the payoff from that light living.

- Going Remote Early. I started taking freelance gigs with me on overseas trips, being that "guy on the beach with a laptop" well before that was considered something you could actually do. Today, you can pretty much start your career there and never see the inside of a cubicle, ever. So definitely jump on the opportunity if you see it.

- Building SaaS businesses on the side, running them until they bring in a respectable developer salary, then ramping down the contracting.

What would have made it better:

- Start the SaaS part earlier. I actually made a few attempts early on, but never followed through to collecting real payments from real users. Instead I build Cool Side Projects of the sort we still (sadly) see lots of here. They were fun. But you know what's even more fun than a Cool Side Project? Never having to work again. Would have been nice to have that happening ten or fifteen years earlier.

- Network better. Life would have been easier if I had an assured supply of high-rate gigs to pick from out of a network of previous employers and co-workers. I burned a few years on the "treadmill" trying to re-bootstrap that after leaving industry. If you can avoid ever having to log in to the eLances of the world, life will go a lot more smoothly.

- Focus on skill & value over savings. I saved a bunch in my 20s, before my bill rate was anywhere near what it is today. Looking back, I probably could have put most of that into personal runway rather than retirement savings. I go back and forth on this one, since I doubt I would have had the confidence to piss off for entire years at a time traveling if the bank balance was really that close to zero.

[1] Capsule summary: ~20 years, startup employee to contractor to traveling dirtbag climber who very occasionally contracted for a few months, to small business owner, to dad with a full time remote contract gig for almost 5 years, to mostly retired small business owner.