I understand getting S80, F80, T72, but I think you should get a FLF80 as your first SO ratchet, or a FL80. These are 3/8 Long Flex and 3/8 Long. I like leverage and find myself reaching for the longer ratchets before the standard F80 or S80.
As far as price goes, here are a few key points. You can usually figure 55-70% of retails is good value and is probably available on ebay with a little persistence. Just about any time you find one for half off you will be able to get your money back or better. Buy any SO ratchet, any condition, any size, etc that you ever see for $20 or less. Ebay is great because of the selection available at any time, but better deals can sometimes be had on CL, garage sales, or flea markets. GJ classifieds is a great source for Snap On as well. Look over ebay completed listings for the models you want to see what they go for.
936 tools (36 tooth) are worth less than 80's. Black oxide or industrial tools are worth less than chrome, engravings also generally hurt value by about 20%.
Plastic hard handled SO tools hold value very well, especially the ratchets.
Happy Hunting