In a little over 30 years of collecting I have collected almost everything at one point in time.
Got the T206 bug when I joined here. Bought around 100 of them before I decided I really didn't care for them. Did the same thing with T210's except I kept the Ft Worth players. Also tried being a pre-war type collector and then sold them.
Have collected 50's and 60's star players off and on the entire time I have been collecting. Have sold traded most of them away for other stuff or different star cards from the same era. Have only ever tried collecting one complete set card by card from that era. Have been working on it for a few years now and am 2 cards away from finishing it. It's a 55 Bowman set with every card coming from a Net54 member. I did buy one complete set from a fellow member. A 1959 Fleer NrMint Ted Williams set I had SGC grade. If not for the amazing condition of the cards I would have never had it graded.
I have also dabbled in autographs from pre-war to present. Same way with memorabilia. Another member got me into collecting bats and now have a decent Wade Boggs bat collection.
My true love and the cards I have always collected are junk era error cards.
From the mid 80's till 2000 I went to a few hundred games. I still get my biggest thrill looking at cards of players I watched play in person.
As far as condition the only thing I care about is the players face has no paper loss or a huge crease running through it. Tape on a card is also something I just can't stand. Writing, creases, paper loss(except on face), trimmed, or centering do not matter to me at all.
I prefer my cards in their natural state. I do have some slabbed cards but they are mainly because one of the grading companies screwed up on the flip.
If it is just a hobby collect anything you like.
If trying to make $ then learn how to pump and dump. I have done both and find collecting for fun really is fun.
Trying to make $ isn't, so now I stick to having fun.