I collect comics and I am in the same predicament as you are. It is very hard to get into any series if you miss too many issues and just try to jump in on issue #30 (or worse, issue #425!). If you try to collect the back issues it just gets too expensive. With that being said X-Men, along with most superheros needs to be started at the beginning for you to fully understand what's going on. Every once and awhile the publishers start the series over again, i.e. Ultimate Spiderman a few years back. Try to find out when a new series is coming out. You can find previews at local comic shops or
newsarama. Deadpool is recently new, but it's so popular that issue #1 is about $6 now. You can still look for One-shots and mini series of X-Men, but you will probably need Wikipedia handy for the story lines. Hope that helps! I'm reading an 8 issue (including #0) independent called No Hero and it's pretty awesome and violent! I recommend it.