Stamps, Ink and Paper are all you need to start! Most stamps it's OK if they're not perfectly aligned, but for a sentiment stamp or when you're stamping one image next to another and want it perfect, I use my Stamp-a-ma-jig. It aligns them exactly where you want it.
For rubber stamps that are already mounted, you're good to go. For clear stamps you would need an acrylic block to temporarily adhere them to.
There are different inks that all behave differently. Dye (water based) inks are good on cardstock. Pigment inks are good for heat embossing and for stamping on fabric (fun!). Solvent inks (like Stazon) are good for non-porous materials like acetate and glass. There are also chalk inks and I'm sure I'm missing a few others.
Inks also usually behave differently on rubber vs/ clear stamps. Some dye inks will bead up on some of the clear stamps, especially the less expensive ones.
It's always a good idea to stamp your image a few times on scrap paper so you get the feel of how much ink to put on the stamp and how much pressure you need. And don't ever "rock" your stamp from side to side! Just press down evenly.
I hope I've helped a little and not confused you more!!!
I actually LOVE acrylic stamps. They are clear and you stick them to an acrylic block. They take a bit less space in general, but you do have to have acrylic blocks for them. They just peel off the sheet they come on and then you stick them to the block. It is nice too because they are completely see through so you can see how they are lining up better.
Sometimes they stop sticking to the block as well, but generally gently washing them with soap and water will make them sticky again.
My favorite brands that I have tried so far for acrylics are queen kat designs and close to my heart. Close to my heart can only be purchased through a consultant though.
Acylic stamps are great for layering images because you can see exactly where you're stamping. Rubber stamps are great for very fine designs that have lots of detail. The rubber doesn't tend to spread out when you press down, like acrylics can (depending on how soft the acrylics are).
Taking a class is a good idea and buy a couple of each kind to see which you like. I'm still a big fan of the acrylic, but I prefer the rubber stamps when I have smaller, more detailed designs I want to emboss.
I said for a long time that I would draw the line and never get into stamping. Oh well - too late! Once you cross that bridge, you can never go back!
I like using rubber stamps now more than my acrylic stamps. I think it's just because the rubber stamps are within easy reach, but I've also found the cutest stamps that are wood mounted. For some reason I can't find the same things in acrylic stamps but maybe, as time goes by, they will get there.