Back in the day, my band was booked through East Coast Entertainment. They generally took about 15% but they were able to book gigs and promote us way beyond what we would have been able to do ourselves. Unless the business has radically changed in the last decade, a GOOD booking agency is a must. Even for local gigs when I was in a local cover band, you just wouldn't get into certain clubs unless you went through one of the big (in some cases just one) of the predominant agencies in that area. It certainly can't hurt. If you are good, the more you play the better things generally get including the pay. It is certainly worth the standard 15% if you are playing more dates and building an audience and recognition. It doesn't matter if you are making $300 or $1500 per gig, imo it is money well spent (yeah, I know agencies are blood suckers sometimes but you gotta pay the dues).

Peace,
TC

If it has strings I will find a way to play it!

You can hear my tunes at https://soundcloud.com/tc-gypsy