Freelance is a tough lifestyle. Regarding booking gigs- it depends on where you are living/working. In my area, it's not uncommon for SMs to book in Jan-Feb-Mar for the coming season (starting in Aug). So it's easier to see ahead of time where your gaps are, and work on filling them. (I've posted here before about the difficulties of filling those gaps, but that's a whole other issue). If you can find a flexible job that you can use to fill gaps, so much the better- but finding a job like that can be difficult.
Or, you can fill them as work comes up, with workshops and sub gigs and other small projects. I think it all comes down to budgeting- if you manage your budget well, you can afford to have a week or two (or more) between gigs without going broke.
Regarding taxes,
[caveat- I am not a tax expert, I'm just getting this info off of the IRS website] it depends on how you get paid. If you expect to owe less than $1000 when you file your return, you can file your taxes once a year like most people do. (This is usually the case if you are paid with a W2, and taxes are taken out before you receive your check).
If you expect to owe more than $1000, you need to file quarterly estimated tax payments, as you are considered "self-employed". (This usually happens when most of your income comes through 1099s.
The IRS website has info on who needs to file quarterly taxes, and how to do it. I've been freelancing for about 10 years. Some years have been easier than others- things line up well, and I don't have to take any "other" work. Other years I've had to be more creative- doing side projects, or branching out into other areas (I was the interim manager of a costume shop for a few months, while they searched for someone to fill the position full time.)