Experience is everything, especially if you are young. The industry will eat you up.
The part of your brain that allows you to assess risk is not fully formed until you are 25.
You need someone who has taken the right decision's before and understands the variables involved.
I remember our band had a few managers headhunting us and one guy in particular who came around to our band house very keen. We thought he was a bit dodgy on first impression. He was very pushy and boasted what he would do for us. He learned we did not have a PA system. He asked, "Do you need a PA? I’ll get you one". He went away and came back with a full PA system for us within four hours.
What did we do? Being idiots, we blew him out. Yeah, easy to judge now. It was one of the biggest of our many mistakes.
Great managers like Led Zeppelin's Peter Grant would allegedly hang promoters out of windows if they didn't hand over receipts at the gig. Now that is the sort of commitment you are looking for in a manager.
Wikipedia says of Peter Grant…
his intimidating size and weight, confrontational manner, and knowledge and experience, he procured strong, and unprecedented, deals for his band, and is widely credited with improving pay and conditions for all musicians in dealings with concert promoters
That’s who you want! No, not Britney Spears Dad but don't be too picky.
Conclusion
My point is you need help, you don't succeed from inside out. People who know how things work and can guide you. An agent and a manager is the next best thing to a celebrity parent, landing one should be a priority BEFORE you sign a record deal.
Talent factories have always existed. Motown taught their artistes how to dress, dance, and present. If you can infiltrate the latest hit factory, you’re made!
You’ll meet many musicians who will tell you that you don’t need a record deal, you just do it yourself online. How are they doing? Bottom feeders mostly. Yes, do it yourself - but only so you can get a deal.
You don’t want the demoralisation of bumping along the bottom, you need the quantum leap. You may never be an overnight sensation but if someone can show you how to leap over the next ten stages, let them! Paying your dues was always overrated.
You're not looking for a friend when you're looking for a manager. They'll exploit you, it's in their DNA, but at least there will be something worth exploiting!