yes ewc is important fresh ewc is the king of all microbial innoculants and soil conditioners in my opinion and keeping a worm bin is so easy you would beat yourself up for not doing it sooner if you ever tried. just toss all your leftover veggies and fruits and coffee and tea leftovers and they will give you pure black gold in return.
blumats are good too but if you are gonna connect it to a live faucet you should get some security equipment to cut the water flow in an event of runoff which can happen. and if you are gonna connect it to a tank be sure to have a tray or something to keep the water from flooding the house in an event of runoff again. especially keep all the electrical equipment off the floor.
pumice is not a necessity you can use lava stones or perlite or rice husks or many other materials.
as for using your own compost as a general rule of keeping my indoors pest free i dont use anything from outside. bagged stuff is usually sterilized which means it will more than likely not contain pest eggs and seeds but your own compost probably will. you can sterilize it yourself by baking it or something but you have to look that up yourself. its a suggestion from an ocd guy