Turkey baster you should be able to get them from $2 or check in supermarkets where they sell kitchen things, pans/bottles/sieves etc... The $2 shop in Manners Mall has them
No matter how big or small the pebbles, if they are slightly smaller than your axie head he will swallow them and they will build up in his body.
You don't have to have anything on the tank floor bottom, you can have it bare, tho some people prefer something.
I have sand in my tanks, but check out the following link as it is a good alternative but for permanent substrate (either gravel or sand), my sister did her tank like this after spotting this thread:
http://www.caudata.org/forum/messages/793/77098.html?1170154180 and if I could convince my husband I would do the same to some of our tanks using sand.
You need aquarium silicone which you can buy from hardware stores, about $15 for a small tube, or buy one online (on TM someone sells big tube for $11, but you need one of those pistol type thingy to push the glue out - geez can't think what they're called and husband is out so can't ask him)
One thing with bare substrate/tank floor you can drop bloodworm cube and worms and it will be easy for cleaning any uneaten food and waste up!
As for earthworms, if you have a garden, since it rained tonight go out with a torch and lift up any pieces of wood/furniture pot plants and you will find worms directly under. It's a bit harder when it's been hot during the day and everything's dry unless you have a compost.
Otherwise might pay to check with places like Bunnings, Mitre 10 or garden places or check on TM as a few people are selling pots of compost worms which you can start wormfarms with.