I've had a successful career as an independent consultant for the last six years and in my experience branding hasn't been a primary concern at all. As @brudgers already pointed out, sales should be your top priority. Until you're fully booked you should be speaking with friends, acquaintances, and strangers every single day to find work. Your next priority should be delivering the absolute best work you can, so that you can stop making cold calls and start fielding inbound leads. Your past clients are your best source of new business. Even better, keep your clients long-term so you're not kicking off new projects all the time.

I don't think this matters as much as what I mentioned above, but I'll answer your questions:

* Maintain your LinkedIn, Twitter, AngelList profiles just enough to back up your credentials when a potential lead google's your name.

* Don't waste your time blogging unless you plan on committing to being the "go-to" individual for a very niche technology/service. You'll read successful content creators advising the opposite, but for each one of them there are 1000 who never got traction, didn't publish anything valuable, or simply gave up.

* Your most important asset is your reputation

* Use your "personal brand" for as long as you can (i.e. until you're hiring other people). Building a reputation is hard enough, don't make it harder on yourself and others by adding misdirection when it's really just you behind the curtain.

* My niche for the most of my career has been "early-stage startup needs product-minded engineer to wear many hats". There has never been a shortage of rewarding work for me, but your mileage may vary.

Good luck! Happy to chat some time if you want to dig deeper. Contact info in my profile.