Here's a link to the welcome & help center which gives directions & info. on everything asked on this thread.
http://garden.org/forums/view/...
Becky, no, the microbadges serve no purpose than letting others know the things that interest you and....they're fun.
The thumbs up are mostly just to let others know that you liked what was in that post, or approved of it etc.... EXCEPT, you never know when there will be perks to accumulating thumbs ups. Recently, Dave awarded a special microbadge to people who got X # of thumbs up answering questions in the "Ask a question" forum. No one knew he was going to do that so it wasn't something we worked for; we were just being helpful to the best of our ability & we got a surprise reward.
