What I did was to start with a type collection of sorts.
T205
T206
T207
33 Goudey
34 Goudey
35 Goudey
36 Goudey
39 Playball
E91
And eventually
T201
T202
E90
Am N172 (Old Judge)
A couple strip cards.
If you pick them up in VG, maybe Vg-ex ungraded you can handle them and get a good feel for the cardboard, and what an untrimmed one feels and looks like. It's even less money if you look for commons with maybe a bit of back damage.
I picked up beaters of all of those before I was 18. Of course it was a bit easier back then than now IF you lived in a town with a card shop. I eventually spent for a few nicer condition cards once I got a part time job. (Should have bought more nice t206 commons and maybe fewer beat ones. If it's "investment" save up for better cards of stars)
I finally bought an second T207 late last year/early this year. So now I have 2 Although if you could see the first one you might disagree.
I was also lucky to pick up a handful of really beat George c Millers and a T204 that wasn't bad. And a truly awful condition T3. Plus a T222, helmar and Piedmont stamps and a silk.
That makes for a pretty decent prewar type collection.
I collected postwar right up to the then new stuff, as well as other sports and non-sports. Sort of still do, just not all at the same time. I'll take breaks from one set and look for some cards from a different set or sometimes just run across something I like.
Steve B