Reddit mentions of StudioFX SANDBAG Sand Bag SADDLEBAG Double Zipper Design 4 Bags Weight Bags for Photo Video Studio Stand by Kaezi

Sandbags. I get sandbags that grips use on movie sets, and just lay one over the legs. Something like this:

http://www.amazon.com/StudioFX-SANDBAG-HEAVYDUTY-SADDLEBAG-DESIGN/dp/B00CXUT5ZG/ref=sr_1_2?ie=UTF8&qid=1395593829&sr=8-2&keywords=Sandbag

As most people here have mentioned, paper is going to be the easiest to deal with for solid colors. The best thing about paper is that if you scuff, crinkle, or tear it, you just cut off that section and unroll it some more. It's cheap enough to not worry about, and super-easy to work with. No cleaning (like vinyl), and no worrying about permanent footprints. A 36-foot roll of paper in most colors will run you about $40 for 53" or $60 for 107" width. You mentioned groups, so I'd recommend a 107" roll to avoid running out of room. 53" is really just for individuals, groups, and pets or products. Here are a few other things to consider:

Are you always shooting at home, or does your backdrop need to be mobile?

I have two sets of triple-rollers set up in my studio. They can be found for around $70 on Amazon, and can be wall-mounted or ceiling-mounted. Each set lets me mount 3 different rolls, and I have one set for 53" rolls and one for 107" rolls. If I want to switch colors, I just pull on the chain to raise one and lower another. To swap out a color, it only takes a couple of minutes.

For mobile situations, get yourself a backdrop crossbar and a pair of light stands. If you only use them once in a while, you can again find them on Amazon for around $40. But if you plan to use them consistently, I'd recommend getting something sturdier. Westcott makes a really nice 13-foot stand for around $80 each (you'll need two), and their crossbar is around $90, though some cheaper crossbars can be found for roughly half that. You can spend less on a smaller stand, but I wouldn't recommend it; anything smaller or cheaper loses a lot of stability. These stands will last you forever, are still cheap enough to not worry about it too much, and are fully usable as actual light stands in case you decide to start working with off-camera lighting later.

Safety

I'd also recommend 2-3 sandbags for each stand to reduce the risk of someone kicking them over. We live in a litigious country; don't get sued. You can buy empty sandbags pretty cheap (about $20 for 4 on Amazon) and then fill them with $5, 50-lb bags of playground sand from your local hardware store.

How are you using your backdrop?

For either of these scenarios, you'll need some way to keep the background down, as it tends to curl. Your local hardware store carries simple spring clamps for about a buck apiece, and 3-4 of those at each corner and in the middle will keep things stable. I'd recommend picking up a few extras as they're crazy-cheap, and great for keeping your backdrop from unrolling if you aren't using a roller system with resistance.

If you're looking for something seamless, you should also consider a roll of gaffers tape (or blue painter's tape, if you're trying to save money) to keep your paper on the floor, in case you want to create a sweep. In case you aren't familiar with this term, a sweep is where the background makes a rounded, 90-degree turn at the floor, resulting in a seamless background with no "corner". It's how you get those images where your subject is isolated against a background.

What it'll cost you, total

All-told, your total cost for this setup (doing it "right") is going to run you about $300 for your supports (including clamps, tape, sandbags, etc.), or about $100 if you go with the wall/ceiling mount. Paper rolls aren't included in this. This is about as cheap as it gets to do it "right", unless you're looking at an entirely DIY solution... at which point the price can drop to 1/10th of that.

Alternatives to paper rolls

If you're looking for more interesting backgrounds, you have three main options:

• dyed muslins
  
• printed/painted muslins or vinyl
  
• gelled lighting on white paper with a spare flash
  
  Dyed muslins will start at about $40-60 and look like these. Printed or painted ones (muslin fabric or vinyl start at $60-100 and go up from there. But if you have a spare flash, you can pick up the Rosco Strobist Collection of gels on Amazon for between $10 and $20, and then have any color background you want, with a nice, smooth gradient. You can toss it on a backward-pointing light stand behind your subjects, or backlight the backdrop from behind. Note that your camera and flash will need to support wireless triggering to do this, or you'll need some radio triggers.
  
  What you get out of your setup depends on what you put into it
  
  You can do some really interesting things with just a simple white backdrop. The biggest factor is going to be how much time you put into learning how to use it. Here's a post to get you started. Note that this article also has a link at the end to a second article about how to create interesting backgrounds using random objects in front of the flash. Definitely a good read.
  
  Good luck! :-)

Most tripods have a hook to add additional weight which can help with stability. If not you can still use sandbags to help.

We had this problem and I actually bought some sandbags to weigh it down so they couldn't move it. Not dirty outside ones, but nylon bags for putting sand it. It worked really well.

Edit: these are what I used. Saved us from drilling holes in our walls. [bags](StudioFX SANDBAG Sand Bag SADDLEBAG Double Zipper Design 4 BAGS WEIGHT BAGS FOR PHOTO VIDEO STUDIO STAND by Kaezi https://www.amazon.com/dp/B00CXUT5ZG/ref=cm_sw_r_cp_api_i_ryojDbQSA6FND)