Your Painting Surface
As a beginner, it's difficult to decide how much to spend on your painting surface. On the one hand, your painting is only as durable as what it's painted on, and it makes sense to spend a little more money on ensuring your time and effort aren't wasted on poor quality materials. On the other hand, you might feel more free to experiment if you're not worried about wasting expensive paper or canvas. It's up to you.
You can use stiff paper or wood panels, but I would recommend starting on canvas panels (below left) which are primed canvas stretched over stiff paperboard. Canvas panels are much less expensive and more durable than stretched canvas, but still give you the canvas texture that looks so professional. You can hang it on the wall nicely without a frame by attaching string or wire to the back. I would recommend starting in the 9" x 12" size for your first painting, and working your way up. A 9" x 12" canvas board costs about $1, and you can paint over it once or twice with plain white paint and start over if you want to.
Most acrylic artists eventually graduate from canvas panels to stretched canvas (above right). Stretched canvas is wonderful to work on because of the way it springs back when you press down with your brush. Stretched canvas is more expensive, at about $8 for a basic 9" x 12". In my opinion it's worth the extra cost, but if the cost inhibits you from trying new techniques at the beginning, you might want to go with canvas panels and just enjoy yourself.
When you start looking for stretched canvas, I recommend pine or hardwood stretcher bars if possible. There are cheaper canvases made with tropical wood from overseas, but in my experience they tend to warp more when your paintings move to dry climates. The thicker the stretcher bars, the more resilient your painting will be.
Framing
Acrylic paintings can be framed, but if you buy canvases with staple-free edges, you can display them unframed with nice results. I don't frame my own paintings at home. To create a finished appearance on a framed painting, you can just paint the edges to match your painting (as if the painting is going around the corners), or just paint them black.If you do choose to frame your canvas, make sure to get an open frame with no glass in it.
My Portraits
My portraits are painted on professionally stretched 10 oz cotton canvas with sturdy 7/8” pine stretcher bars. The canvas is stretched and fitted around the edges of the stretcher bars, so the portrait can be displayed attractively without a frame.
This canvas stretching technique is called spline-fitting, and it has a smooth, finished appearance at the back, with no staples or loose canvas showing. The edges of the canvas cloth are tucked securely behind a fitted rubber strip.