I have large flat bubble stones about 5in. long.  They dont stay put.  Also my plastic plants float up constantly. What can be used as a weight to hold things down.  Most metals would be dangerous.  I would think quartz or flint rocks would be safe.  I was thinking a stainless table knife tied to the bottom of the bubbler stones w.nykon fishing line would not be a contamanate to the fish.  I also have some of those stones from a California beach that are black and smooth ,obsidian i think.

Any suggestions?

One. Gravel?

And there are plenty of really nice live plants to use, who will take care of themselves once they root in the gravel.

When using those plant weights, it's the kind you wrap around the stalks, right? It's usually a good idea to stick a thin piece of foam between the weight and the stalks That's how most plants are sold here either way, and I've saved a few of the "wrappings" just in case

On live plants is it better to buy grown plant or the dried packet of bulbs?

I only ever let the weights be on the plants temporarily in case the plant in question didn't have roots yet. Just because I don't want to close the plant roots into anything, be it pots or weights

There is a reason the fish start moving the gravel: It's their natural behavior. And personally I don't think a fish can be happy if it isn't allowed to do what it's supposed to. Goldfish in nature dig through the mud to find edible insects and worms, I think it's very important that you try and mimic their natural environment at least a little if you intend to keep fish. (By choosing plants that would grow in their original habitat etc, but that's more a case for people keeping fish that are found in the wild.) Why is it even a problem though?

I think getting whole plants are the best, I mean how do you even intend to keep your goldfish from eating the small ones? Rather look into some different kinds that work to keep with goldfish and buy some of those.

And you can edit your posts instead of adding 3

That's always useful of course For some reason, these tall things I have now stay really well in place, all I did was add a little wall of pebbles around the roots so the goldies wouldn't be digging too close

I've had to move some plants to my tropical tanks because my goldies kept digging them up....ces't la vie

You can always use silicone and stick some ornaments together, like driftwood and slate? c:
I think that would be better than quick cement c:

Limestone should be avoided since it will be changing the water quality.

Don't pick anything up from next to the road, that's most likely polluted with all kinds of stuff you don't want in your tank.