It sounds like you're new to anal; I wouldn't recommend being too ambitious as far as size for your first toy. I've been mentioning it a lot, but the silicone buddy plug from vixen is a great first-time toy, especially for a guy. It's got a slight curve to touch the prostate. Pair it up with a good water-based lubricant like maximus, and you're in for a lot of fun!

You should probably try to go for a small glass dildo. I found that the weighted feel, and hard material feel best. IMO they are better than silicone, although many could argue otherwise.

Something soft is what I'd go for first, too - especially if someone else is going to be "driving". Until you (either singular you or plural, couple-you) know how your personal anatomy goes together you could do something with a stiff dildo/plug that could be uncomfortable (or worse) - I've even gotten a bit carefree and wild in the heat of passion and been a bit sore for a while with a hard probe.

My advice would be something that starts small, doesn't get too much bigger, and doesn't have too much texture to start with, then move up from there. A number of the beginner plugs can also be used for thrusting, which make them good starter toys (the bad side of that is that they don't tend to stay in as well, so you might need a hand now and then if you want them to stay in one place).

Start with silicone first, I started with glass and didn't like it and stayed away for awhile. Then I tried silicone and now I love both silicone and glass and both are easy to clean. You can also get silicone that is soft or firm your choice, with glass their is no choice.

I'm somewhat partial to slender probes, especially those that become slightly larger down the length of the toy. Your best bet, however, is indeed to stick with silicone or another material with a little "give" - TPR silicone is alright too, though not as safe as pure silicone. I would recommend staying away from anything that says "jelly"; I've found that, besides not being very safe, these items are rather "floppy" for penetration.

I've got to recommend a toy that I just bought this week. It's called Aneros Peridise and it's fantastic. It's smaller than the other Aneros plugs so it's easy to insert and feels comfortable for long-term wear.

I would recommend starting with something like the Tantus Little Flirt, then moving to a slim dildo or medium sized plug. I've had a bunch of different toys over the years. I find that it is best to have some variety to match whatever mood your in at that moment.

I know this was an old discussion but I thought it was a good one to bring back up.

so much variation, i enjoy a tapered plug then move on to a p-spot massager

Well, if one is new to anal play, I think the easiest thing to start with is a soft plug. It allows the body to get used to the sensation of having something in the butt before there is the added sensation of thrusting in the butt.