If you haven't used a pad before then I can believe that you were freezing your butt off. I've done that once or twice and it wasn't fun. The cold ground really sucks the heat out of you.

I think it takes some experience to figure out the best pad strategy. It's not the same for everyone because it depends on sleeping position, etc. There is something of a tradeoff of warmth vs comfort also. A closed-cell foam (CCF) pad is great on insulating you from the cold ground but not so much on comfort because it doesn't compress very much. It protects you from pointy objects under you but it can't turn hard ground into a soft bed. An inflatable pad is more comfortable but less insulating because the air inside circulates between the warm top (where you are) and the cold bottom.

If you can deal with the CCF pad comfort then the next question to ask is about length. You really only loose significant heat through your torso so a short pad is probably sufficient for insulation. However if you sleep on your back your heels will get a bit sore (and maybe cold) from resting on the hard ground. Make sure you put something under them.

CCF pads like the Ridgerest and Z-lite do eventually compress from use but I'm not sure it's that big a deal. And they're cheap so if it only lasts you for this one season then who cares? The Walmart blue CCF pad (the eggcrate one) is nice and wide and costs like $12 or something. You can cut it down to the size you want. Get one and try it out. If you don't like the CCF pad then you're only out $12.

I know less about inflatable pads. I do own one but I find I don't use it much. It's self inflating (a therm-a-rest) and it doesn't seem that much more comfortable than the CCF pads. I think the thicker pads that are not self-inflating are more comfortable. Some have insulation inside (Big Agnes is the brand I hear people talk about the most) to keep down the convective heat loss but I haven't tried then yet so I can't say. These are more expensive so you want to make sure you really want one before shelling out the bucks.