OP, the thing with 'trendy' is that it changes and evolves all the time, so unless following trends and fashion is something you enjoy and comes naturally, it's always going to be more of a stress than anything else.
The great thing about @lexiepuppy's list, and what I THINK @damnthatanxiety was trying to get at, is that it's not 'trendy' as such, because it's not based on a come-and-go fashion. Instead it's full of classic, stylish basics. Fab, solid, simple foundations.
I'd recommend you start there – and don't underestimate what's already in your wardrobe!
Literally AIM for plain, simple outfits at first - like the basic blank canvas to work with, or the foundations of a house.
Once you've got them, then start to just play with accessories: hats, glasses and sunglasses, scarves, jewellery, watches, gloves, belts, bags, shoes...
They're cheaper, more versatile and re-usable than clothing items, and don't mean you need a whole wardrobe rehaul as soon as some twenty-something instagramming fashionista decides that baggy crotches are back 'in'.
You'll notice something of your own personal style emerging from the type of accessories you're drawn to – the ones that you add to your basic outfits and think: "Ooh, I feel like myself now!".
A simple 'white tee and jeans' foundation will look totally different on me vs my best friend. She'll add big diamond drop earrings, lots of eyeliner, a brightly coloured handbag and heels, while I'll roll up the legs of my jeans and add a bowler hat, little backpack, my glasses and a long cardigan.
You could wear a white tee and jeans every day for a week and style it completely differently each day with your accessories and extras. So I'd really recommend starting there if you're just experimenting with what looks and feels good to you.