I think Arsenic is a material, not a commodity, isn't it? In other words, no I don't think you can mine for it.
Ice mining is probably only really worth it if your sales port is in Boom state, and you can pick up missions (high tech systems often yield mining missions too). Myself, I tend to go mining first, fill up the hold then, when in port check the missions and accept the ones I can fulfill immediately, for a bonus with what I've got onboard (less stressful that way).
Advice is right, Metallic is the best yield followed by Metal Rich, lastly Rocky. I personally wouldn't bother with prospector drones much, though in a Clipper I expect you can afford the slots. In Python, I use two collector module plus 7 slot refinery, medium laser, it's all powered off when I'm away from the mining site. I carry discovery and detailed surface scanner (also have SRV aboard for excursions) but it really is worth taking the time to find a Metallic ring (try searching for mining threads in the forum here for known sites if you prefer). You are supposed to get a better yield at the RES sites but I tend to go african and park away from them. Outside the bubble where I work, with KWS scanner being mandatory, if you've no cargo aboard you can decide whether a bounty is worth engaging any NPC's you encounter (if you do have cargo they WILL attack) but, after initial contacts when arriving, you'll be left alone after that and can relax pretty much totally.
It's a slow and steady operation mining, best done while listening to the radio or something but if you do a couple of runs to get the feel of it and organise your refinery, there are a few tricks to filling up your hold faster (eg. bust open the asteroid, then move your ship so the cloud of fragments is roughly where the limpets line up to enter your cargo scoop. The drones will clean up in seconds) .. In other words it is possible to "get good" at mining so it's something I do quite a bit, as steady predictable money plus a few bounties here and there are fun to collect.