No, no, no, pls don't put stones/pebbles in the bottom of the pot.

It'll interfere w/ the mix & its proper drainage, which is the WHOLE POINT of using it.

Best to get correctly sized pots for the plants. I'll let others try to explain that.

You have found one downside of big and deep pots already- it takes a lot of soil to fill them! I am not totally sure of the negative effects of a big pot, but for succulents, which often have pretty small root balls, a huge planter just isn't needed!

A good mix is more forgiving for most succulents if your pot is oversized. However many succulents are sensitive to over watering and will do poorly.

Other succulents such as Mesembs (Lithops, Fenestraria, etc.) are extremely well adapted to absorbing water. So much that if the pot is too big and there is too much water they will split/explode/rot.

Choosing the right size pot will make your life easier and enable your succulents do better. =)

If the roots are 2" long and the pot is 6" deep, you have 4" of soil which will be wet but of little use to the plant. It's not going to dry out quickly either. Depending on the plant and the circumstances, rot could develop from that overly wet soil. Small plants don't grow into oversized pots. Remember succulents have fat leaves because they store their own water in the leaves.

Look at the pictures on "Succulent Craze" thread to see some nicely potted plants, other threads too. Note that they are not potted too low either.