I grew up in the 80s and 90s hearing the Mantle legends, so when I looked for something to focus on, I chose the PSA Mickey Mantle Master Set registry. In only a few years, I've now got about 150-175 different Mantle (and Yankee team) cards from his playing days (1951-69). Many you can buy for $20 each in VG, many are going to cost thousands.
But I'm having a lot of fun with it; got this banged up Bazooka this morning for $70:
1965 Topps Bazooka - [Base] #1 - Mickey Mantle [Poor]
Courtesy of COMC.com
Front is pretty clean (although cut poorly, common for the cards), but the back is destroyed. Will still get a PSA Authentic and go in the collection... ;-)
Adding a couple every month I enjoy more than saving $3,000 over the year and trying to buy one card at the end.