Just throwing in some of my own experience. I come from a family of women who sew, but only picked it up as an adult. When I started I sewed at my mum's house so I could get advice :)
Pick your projects wisely. Sleeveless tops and skirts are great when you're getting your head round seams, reading patterns etc
I like using dress patterns - simplicity tend to grade theirs for beginners. If you can find a class on reading patterns, or a friend who dressmakes, that's helpful. Don't start with a vintage pattern. The hours I've spent looking at some old school pattern going 'eh'? Even stumped my mum with forty years dress making experience. It's one of my fave tops though (one of my grandmas old patterns).
Second, fit. I confess I rarely do a muslin - it depends on the garment. Because I wear more than a b cup (the size most commercially bought patterns are made for) I have found doing something called 'total bust adjustment' :D really revolutionised how tops fit. Here is an intro to fitting patterns thethriftystitcher.co.uk/the-best-way-to-make-commercially-bought-sewing-patterns-fit-you/
Fabric: start with woven not knit fabrics. It's just so much easier to work with. That means cottons and polycottons, rather than jersey. There's loads of fab prints out there though. This also means working with a pattern that suits cotton (it will say in instructions or on back of packet) I'd also avoid working with sheer fabrics initially.
When you get to a bit of technical stuff - seam, turn under, etc, google it. There are loads of great step by step tutorials for each part of garment construction. I worked out how to do a blind hem thanks to a blog.
Machine - I have a fairly basic janome and I've done everything on it. Garments, curtains, even free motion embroidery and quilting. I am getting a bridesmaid dress altered and the dressmaker has the same machine! Good quality but doesn't need bells and whistles.