In response to some of the questions I have been asked, there are 9955 players who debuted between 1946 and 2011.
With regards to new players, I look at
http://espn.go.com/mlb/debuts everday to see what players made there major league debut. I then look through my minor league autographs to see if I have them. If I dont I write to the player in care of the team. I usually wait about a month for them to respond and if not I buy the autograph. For instance last night 3 players debuted, I have Matt harvey and Starling Marte, but need Jim Henderson, so I will write to him this weekend. So technical it will never be complete.
Why did I start with 1946? Well around 2000 I started writing to players. I had purchased a debut list from Jack Smalling, which has what players debuted every year. Every time I would get a player back, I would mark him off my list. Over time, I realized more players were alive from 1946 on so thats what I concentrated on. At one time or another, I have written to every living player.
With regards to multi signed items, I prefer single signed. The majority of my collection is single signed, but with the last 10 autos it has been very hard to find on single signed, so I have started buying them on anything I could find. I have 4 autos on team signed balls, and I believe 3 on album pages, the rest are all single signed. If I was able to find single signed items of that player, I would sell the multi signed.
Whats next? I am presently working on a signed 1969 Topps set which I need 36 completely signed cards for. I have begun purchasing autos of the 1940 to 1945 debut players so I am sure I will concentrate on that more as well.
There are just so many things out there to collect, but only so much money to spend : )