I've had YNAB for about a year now and I was doing really well. Then this summer happened and I feel like I totally tanked on savings and anything to do with my money.

I'm trying to piece my budget together again but what I make varies week to week, and I think a percentage based budget would be the way to go but I'm not really sure where to start.

About my finances:

Over the summer I was working a job that while important for my career field was awful pay. I made $100/week and they covered my housing expenses. It wasn't a waste of time but it definitely murdered my budget.

I work as a nanny and make $300 a week minimum but I pick up odd jobs here and there as well, so one week I might make as much as $500 or $600 but a minimum of $300.

Starting in the next two weeks I'll start working at a theatre (freelance). I'll make $35 for every show I work and a $350 lump sum over the six week rehearsal period. Some weekends there are more or less shows and since it's getting close to winter there is a potential of being snowed out.

I just bought a new car that has $270 monthly payments but I try to pay $300 a month on it. I still live with my parents and therefore have no housing payments of any kind.

My car insurance is $30/month and my student loans are being slowly paid off by my parents for the first three years I'm out of school. I'm extremely lucky but because my mom did the same thing with my sister she won't let me start helping pay them off. I pay the interest each month on them which is currently $45.

All of the work I mentioned is w-9 work, as was my summer job (also freelance). I know I have to set aside taxes for that as well.

To top it all off my boyfriend is long distance and about every six to eight weeks we see each other, meaning I buy a plan ticket every three to four months.

I don't know how to calculate percentage based with this knowledge. Do I assume I'm making $1200 a month and go from there? Do I do it weekly? Should I just start throwing the extra money at my car payments?

EDIT: okay maybe I'm phrasing this wrong. I make $1200 a month as my base salary but, for example, I made $1800 in September. What I'm asking is what I should do with the extra money. Should I always put away a certain percentage? Should I throw the extras at my car payment?