What materials do I need?
You don't need expensive / professional quality paints and brushes to start. If you can afford nice brushes, that's great for you, but you can start low, and then figure things out as you go. I used acrylics before switching to oils, and my starter pack looked like this: a 6-piece set of synthetic brushes, a set of oil colours (24 tiny tubes), a bottle of linseed oil, a few small canvases on cardboard support. And LOTS of enthusiasm!
Oil paints are considered "difficult" to use, it's sort of a "professional" medium, but that's a stereotype. I think oils are perfect for beginners, because they're flexible, they don't dry immediately and you can always correct your painting if you made a mistake. They cost more than acrylics, but to my point of view, they leave more space for creative process. And the pigments have more natural, less saturated colour.
So, equip yourself with a bare minimum - a couple of natural hair and synthetic brushes (get medium size, like 8, 10 and 12), paint, linseed oil and a bunch of paper towels.
I know nothing about painting, what should I do?
If you don't have any painting experience or theoretical knowledge about values, colours, perspective (etc), it would likely be useful to at least get a book or watch a few youtube videos on those. However, don't let anything stop you from trying - painting after painting you'll learn to see your mistakes and get better. You can draw and paint from photographs or real life, important is to start. There are a lot of recommendations on choosing a subject and how to crop and compose your painting (check out "Daily Painting" book by Carol Marine - it's perfect for beginners). The internet is full of free lessons, master-classes and tutorials. There are paid courses for beginners too! Anybody can do it, so can you.
How do I decide what to paint?
Easy - paint what brings you joy. What inspires you. What you find beautiful. It's easier to start with still life, because you can paint whatever object you find in your house - your favourite mug, a bunch of apples or a wine bottle. Choose your subject, study it, analyse where the lights comes from and where the shadows are, and that's your first step.
It's better to start small - take small canvases, like 20x20 cm, or around that - this way you won't have to break your head over the composition too much (big canvases require deeper expertise), just capture your subject and if it doesn't come out good enough, you won't regret about ruining the canvas too much. Just throw it away and take a new one and try again.
How do I get better?
Practice. As much as you can. Regularly! Practice drawing, sketching, capturing values, shapes, etc.
Read some theory - use all those available sources online or offline - there's an ocean of great books that can help you improve your skills.
And I know that it's the most rewarding when you finish a painting and you absolutely love it and you can hang it in your home oh so proudly :) However, don't focus on the result. I know it's not the easiest thing to do, been there myself! But try to slow down and enjoy the process, because that's the most important part for a beginner - practice is when you learn and can correct yourself.
Happy joyful painting to you :)