Hey,
Starting out on blender is difficult as is so all the best. If I can offer any personal advise it would be to head on over to youtube and check out a channel called Artisans of Vaul. Absolutely incredible channel with tons of content to help with blender at he early stages and explains things very well too.
With accounts to scale, I don't think I can offer any tips on what correct "scale" we use. It is a tweak off of something called heroic scale. True scale is a bit too thin for our minis.
Our standard human Marine is roughly 40mm-45mm tall if that helps with doorways and such. Other than that i cant really offer anything more helpful.