I'm certain you could learn online.
It is helpful if you know someone in RL who can sew a little bit to show you how do do any fiddly bits. Could you borrow a sewing machine? Or try freecycle. Lots of people have them gathering dust in their loft, you'd be surprised. It's helpful if they have the instruction manual, as the most tricky part is putting the thread on the machine to start with! But google is amazing for tracking down instructions for things.
Curtains are straight lines too! Actually, I have got to make some curtains for my new baby's nursery - hoping the fabric arrives before the baby does, at this rate!
If you can follow instructions, you will be ok. Any technical terms, you can look up on the net or ask here, and someone will explain what to do.
If you can get hold of some fabric scraps from somewhere, or even an old curtain or something from a charity shop, you can give it a go and see what you come up with. You don't need tonnes of equipment, but I would recommend:
A pair of large scissors to be used only for cutting fabric/threads etc. Cutting paper etc with them will blunt them and they do need to be pretty sharp.
A pair of little sharp scissors for cutting small details and snipping threads (really useful though not essential)
A box of pins (definitely top of the list actually)
A packet of various size needles
Tape measure
and you're away! You can add things to your collection as you go along.