Be very carefull of buying cheap anything, you need good tools.
You will need at least two sets of shears: Larger fabric shears, one small set for at the machine…mostly for cutting threads. Good shears cost about $80 or more. Little ones may cost as much as 20-30. A seam ripper is needed. Get a good one or get a couple cheaper ones. Yes, they do get dull.
That said, I really doubt you need much in the line of a machine for silnylon. The small motors of home sewing machines are perfectly suited for up to 7-8 layers of nylon. Brothers, Pfal, and Husqvarna make some fairly good new machines. Don't forget a machine will have other uses. A basic machine with 5-10 stitches will likely be overkill, most will have *many* more. Once a machine is set up, it is rarely changed, except stitch length and tension, though.
Tension, stitch length and type, needle type, thread thickness, top feeders ("walking foot") etc are all interelated. Too many stitches can "score" a fabric making it an easy place to tear. Too few stitches can leave a seam weak and leaky. Try to think ahead and adjust accordingly. Throwing in a few more stitches because it cannot hurt is a rookies mistake.
Keep a chart of your settings for various stuff. Long hems, Heavy over light fabrics, light over heavy fabrics (netting to silnylon, for example.) Cuben fabrics should be both sewn and glued. Usually alcohol is used as a glue solvent. Acetone can be used to clear the needle but may melt some threads/fabrics. Cheap threads will fray and ball up at the needle, good for hand sewing, not machines. Pick one brand you know you can get readily and buy a few spools of black, white and grey. Other colors as needed. But, camping, bears don't care about the thread color. Purely cosmetic. I recommend the 100% polyester, but even cotton is OK, though it can rot over several years.
Look at how things are put together. Your existing gear should show you how to use the various stitches needed for camping. Often, a sequence of putting things together becomes apparent looking at the various corners.
Spend a bit of time on your gear. It should last at least 10 years.