I use a plain 5 gallon bucket with an air stone for the brewer.
Grab a nylon, sock, or fruit (jelly) strainer and put some good soil, EWC, or compost in it and hang it in the bucket. For more microbes, make an uncovered rice wash overnight and add to the bucket.
Add the molasses to the bucket and bubble overnight… that’s the cheapest way I know of. If I add LABS I do it after brewing and right before application so it doesn’t compete with the other microbes.
I’ve seen a test that compares the biological content of many of the supposed microbe products and many of them do not live up to their claims. Probably Photo+ from Microbe Life is one of the better ones at $16.95/pt on their web site. It’s a favorite and standard for folks in the NFTG growers group.
Try going to microbelifehydro.com and request a sample kit. $14.99 for shipping. You can try their options or do some more research and find something that you like better.