Food changes? Gradually or what?

[Barbeque]

My chicks are almost 3 weeks old.
I have been giving them starter feed since I got them last Monday.
I want to know when and what I should give them next?
Should I do it gradually?
What different types of feed will I need throughout their life?
Also, if I may possibly have to build a coop, when should I start?
I have like, $120, and I know that can't pay for a coop, but maybe I could build one?
I dunno, I doubt it. It has to be big enough for 7 chickens.
But if I invest in a nice one, it'll last.
Their brooder is 2 feet by 2 feet.

 

[Gonzo]

The next step is grower... Good luck though, around here, nowhere has such a critter. We keep ours on chick feed until point of lay. Then you'll switch over to layer pellets. If I was you, I would watch craigslist. You may find something on there. I've even seen folks convert dog houses into coops.