What a cute idea. Just turn an appropriately sized cheap plastic pot upside down inside the large- and medium-sized pots and pour soil around them. This creates a platform for the next tier and saves money on potting soil.
How to get rid of snails and slugs. 101 Gardening Secrets Experts Never Tell You>You can also deter slugs by using sand or gravel around the garden. They can't move around without a moist surface. Coffee (caffeine) will kill slugs and snails.
10 *Brilliant* Frugal Gardening Tricks When planting, leave the tp roll a bit of it exposed. It not only helps to guide the plant upright but more importantly keeps the bugs away + label each roll with see variety to know what's what
This is a MUST READ for anyone growing tomatoes. There's LOTS of science behind this planting plan that makes super healthy plants. Links give even more advice/ with pictures. -awesome article on tomato growing