Were I to dress like your friends mum, I would look absolutely ghastly, I have a pale, almost pasty skin colour and I would look like a Dracula's victim, when he had sucked them dry. I learnt a long time ago not to wear black.
Start, if you can by making sure you are a healthy weight, which you may already be.
Next, a lot of style comes from within, how you walk, how you talk, what your mindset is. So if you want to be stylish think about who you are.
The other thing is to consider your shape. I have next to no waist, and never have had, so I avoid clothes which cinch me at the waist, preferring looser dresses and tops or those with a raised waist. I have long legs and (still) make the most of them.
After that just wear the clothes you feel happiest in because you will then feel confident and outgoing. Don't sweat the small stuff.
My personal style involves colour, mainly autumnal and jewel colours, lots of straightleg and slimline trousers and colourful tops. I am currently wearing fine dark brown cords and a burnt orange plain wool polo neck sweater and large bronze pendant on a long chain round my neck. Am I stylish? I have no idea but my DDiL and 13, nearly 14 year old (the most critical age) tell me I am.
Looking stylish has got nothing to do with aping other people. It has to be what you feel confident in.