How much do those rings set you back connect? Also do they take much work to turn into bases?
Usually about a buck each, give or take a few cents. Quite cheap for adventurers and squads, but probably not economical for armies. The hard part is finding a consistent place to buy them, then hoping they have ones of the right size range in stock. I usually find them at souvenir shops and gift shops, and buy a handful opportunistically when I come across them so I'll have stock at home when the need arises, rather then trying to seek them out on an as-needed basis.
To prep I put a piece of masking tape across the bottom, then fill with 2 part epoxy glue to about 1&1/2mm below the rim. Once the epoxy's cured, I remove the tape from the bottom, and use that remaining 1&1/2mm to sculpt my groundwork with epoxy putty. I aim for average ground level to be flush with the rim, but the 1&1/2mm gives me room to make negative shapes if needed for more realism. I trim the slotta tab on the figure down to just pegs under the feet, then trace and drill holes for the pegs in the groundwork.
I've also used the same technique on napkin rings and bracelets to make plinths for display figures and vignettes.
Actually, gimme a sec and I'll post a pic or two. *EDIT* Camera battery's dead. Pics in a couple hours instead, I guess.