Gaining

You can gain a great deal of weight without a feeder. You say you would gain for a feeder how about gaining to prove to your potential feeder that you can get fat? Don't worry that they will miss out on some of your gain because you will still be mobile when you meet them. They will fatten you beyond all capability of you to do anything for yourself except eat. You will be as helpless as you are in your avatar. So stop dithering about and get on with your life. You know what you want so do it.

I've never had a feeder in my life and I went from under 100 pounds when I was 12yo to 245 at 16yo. You definitely can gain without a feeder as long as you can motivate yourself and stick to it.