I'd say that as long as the hiking/boot socks weren't bright/bleached white they'll look fine. Isn't there a picture of Ewan MacGregor sporting the kilt + boots and normal boot socks scrunched down?

I agree that a sporran looks nice with the kilt, so maybe you would like to use some of your money on the sporran. But to me it's not necessary. It really is a bit of opinion. Maybe try and find pictures of people with and without the sporran and see how you feel about it.

What downside could there be to wearing a tartan that has personal meaning to you? Doesn't mean you have to restrict yourself to one tartan but it sounds like a good first kilt choice.

Anyway, since you'll be wearing this mainly for you and not for an event, so don't worry too much about the kilt police. You'll never silence all of them anyway...