A ground cloth for any tent is a really, really good investment.
They stopped calling them 'ground cloths' at some point, or whatever, and started celling them footprints. Why? Who knows. Tents dont have feet, but whatever.
YOu can probably find one to fit whatever tent you have, and they run 30-50 bucks. They are made to keep the ground moisture out of your tent, and to keep sticks and rock from poking holes through your expensive tent floor. I have only ever replace one ground cloth because of wear, and that was after a few years. They are well worth it. Tent repair kits never make it as good as it was, and ultimately are not as good as just going the cheap rout and buying a big (bigger than the floor of your tent anyway) heavy duty tarp and using that.
The one good thing about a footprint is that they are designed to fit specific tents and often line up with the stake straps of the tent they are made for. Make sure if you use a tarp that it is tucked in just slightly under your tent, otherwise it will collect rain water and act like a nice little pool. Which is good if you are an amphibian.
A camp pad is good for smoothing out the ground a little, and insulating you from loosing all your body heat through the floor of your tent. They are about 5 buck at Walmart. More expensive options like air mattresses, are also good, and often yield better results in both comfort and heat preservation.
Reflective blankets are also not that expensive and go between you and the ground helping to keep body heat in. Personally I never noticed a difference with or without one, but I know people that swear by them, so yeah.
There are also portable heaters that run on gas canisters and batteries, that are suitable for small tents, but add the responsibility of making sure you are not a tool and don't set your tent on fire. Its not that difficult to ensure the safety of both you and your tent, and with a small tent they do a damn good job of warming the place up.
A fantastic resource for all of these items, and all sorts of other camping gear that you never knew you needed, is rei.com.
You can also look up stuff there, and then Google the name of the item to see if someone else has a better deal.
I also heard rumor of tents blowing away. usually because ground stakes are in moist or otherwise loose ground. There are alternative steaks which are actually basically little bag like objects that you put a big rock in (or a bunch of little ones) that replace stakes by just being big freaking weights that keep your tent firmly in place and on the ground. They are often used in snowy locations, where they fill them with snow and then bury them a little under the snow to keep them down.
Anyway. For people planning on staying on site, there are lots of relatively inexpensive options that can make things more comfortable for you.
A good sleeping bag however is usually the best place to start. The little flannel one you got at target is not really going to cut it.