I wrote this guide for returning collectors which you may find interesting! www.elitefourum.com/t/back-into-pokemon-a-guide-for-returning-collectors/13079/1
While I’m not an expert on WOTC cards I would honestly say that you should start picking up mint cards or graded 9s. Not everyone has to collect 10s, 9s are extremely high quality cards for a fraction of the price of 10s. If you want to upgrade to 10s later on that’s always an option! For the sake of starting out you will also get a lot more for your money. Its all about what’s valuable to you.