I would recommend getting measured at a tailor so you know your suit size. Good suits, sportcoats, and blazers can be purchased for great prices on ebay. This is a helpful guide to getting started with suits and blazers: https://www.reddit.com/r/NavyBlazer/wiki/index#wiki_the_basics
This is a good intro as well: https://putthison.com/start-here/ (The writer can be kind of a fag but most of the articles should be good)
Get your neck and sleeve measured as well for shirts, as any dress shirt or even casual button down worth it's salt with be numerically sized according to the neck/sleeve measurements
I try to dress decently, but not stand out, which can really mean a pair of jeans or chinos and a tucked in button down with some form of leather shoes in many cases. When it's real hot out I will wear a lightweight button down, untucked. When it cold I add layers such as longjohns, wool sweaters, and a jacket suitable for the cold.
I would recommend buying some linen pants and shirts secondhand and trying them out, linen is supposed to work well in the heat.
I don't wear any tight clothing, especially not pants. Classic straight fit jeans and pants, relaxed fit shirts. Not only does it not look effeminate, relaxed fit clothing gives you more range of motion, allows air flow in summer and room for layering in winter, and is just more comfortable in general.
If by moccasins you mean something like these, yes you can wear them with socks
