I'm a recent entrant into G.A, but I have no desire to own either a Cap 1 or Marvel Comics 1.
I like Cap, but like every Cap fan, I have all the Silver Age appearances. If I had a Cap 1, I'd feel compelled finish that run as well, or else it would look out of place. Seeing how many seasoned collectors are perpetually hunting Caps, that doesn't seem enjoyable at all. Knowing what these books sell for, I feel it's too late to start now.
I'm 25 issues into a Captain Marvel Adventures run. There's plenty of supply, and the fact that they're cheap benefits me twofold: one, most of the run is easily accessible, and two, the big collectors only seem to want high grade copies, if at all.
I'll also buy G.A. Batmans. Filling in numbers ahead of my Silver Age issues is adding flavor to my existing collection, so it doesn't matter if I never have the first ten or twenty issues.
Vexsus, if you want an inexpensive golden age title to work on, try Joe Palooka. I had an issue show up in a stack of books, and I enjoyed it. The art was more cartoonish than I was used to, but I found it surprisingly well written. I can't understand why they don't sell.