Probably by straightening your hair first and then curl it using large barrelled tongs. Wait for the curl to cool down and then rake your fingers through your hair lightly to break up the curls into waves. Use a little serum for the shine if you need it, and finish it off with hairspray.
Depends on the brand you choose, generally it costs the same as most other styling products. You only need around 3-4 drops at a time though so it does last for ages.
after your hair's dry i dont think ull need to straighten it. u might wana put the top part of ur hair in a roller or 2 just to give it extra volume when its 80% dry and then blast it with the dryer.
for the curls use a medium sized tong, section and start from the back, spraying with hair spray as u go along.
might look like a betty boo but after u run ur fingers through the curls it'll loosen them
ive never used serum and it look fine without it