Just so you know, you said about your friend being squeamish of live food, expect to find crickets loose in your flat. They can escape from exo-terra tanks I used to find them all over the place when I had cresties, so annoying! I fed mine on some food I ordered from the states, it was a 2 part thing one part base and one part flavour and I can't for the life of me remember what it was! They got dusted crickets and the odd locust too (not all of them liked locusts). You have to be careful when feeding dusted crickets and a food mixture as the mixture should contain a lot of the vitamins they need and you don't want to overdose them.
For a baby crestie that tank will be fine, I would say use kitchen roll as a substrate until it is old enough to catch food properly and not eat the substrate, unless you really pack it down tight. I used eco-earth in my vivs as it helps with humidity.
As you say you will need a larger tank for an adult crestie, 45x45x60 cm exo-terra is the minimum for an adult
they need the height being an arboreal species.
Cresties are great geckos, but I warn you, they are addictive lol I had 6 at one point! Unfortunately I no longer have any though
There are many breeders that you can get a crestie from, don't pay Pets at Home prices they are really expensive
I recommend looking at magnetic ledges and hides for your crestie too, mine loved them