Congrats on attempting hand quilting! As others have said, your stitches will become more uniform and smaller over time. Some people find that having a small sandwich to 'warm up' with before working on your actual quilt helps get them more consistency on their actual quilt.
I use whatever 'hand quilting' thread is the color I want. I don't care about specific brands. JoAnn's sells a brand 'Americana' which tends to be a bit heavier/thicker than other brands but it works just fine. I use quilting 'between' needles. I use a metal 'Thimblelady' thimble that is open at the end, thus you push with the pad of your finger vs the tip. I find this far more comfortable. I also use a round hoop vs the oval. I've bought them at JoAnn's for very reasonable prices. I was gifted a couple of other, much 'nicer', hoops by a quilting friend and find I like my cheapy JoAnn's round one the best.
I've purchased quilting templates from both JoAnn's and my LQS. I've done in-the-ditch hand quilting but find it far more difficult. Besides, if you're putting all that effort into your quilt, your work should be seen!
Good luck with your endeavor. I'm sure you'll do a great job!