Nico Nico Nii!~
New packs don't have any older cards, just new cards from those particular sets, but the new packs do tend to have at least a few cards with older Pokemon.
If you're looking to relearn how to play, then I'd start with one of the Trainer Kits. Otherwise, if you're just collecting, I recommend tins and booster boxes instead, though you can't buy booster boxes in stores. You'd have to buy those from online retailers.