Save yourself a boatload of money and forget the Bondene or SameStuff, Tenax etc. solvents. Go get yourself some MEK at HD or Lowes, works the same. If you need a little bit longer set time, use Tamiya's glue, it's nice and thin but good work time. For even longer you can use the gooey std model cement but it is messy to use in a precise manner but set time is forever.
For styrene thicknesses, use what works for the part you are trying to make. .060 or .080 are great if you dont need curves. Forget trying to bend it unless you want to apply heat to it. You can use .030 or .040 for curves but the solvent will deform it a bit if you are putting it over a frame or forming it to curved pieces underneath. It is a slight deformation but noticeable (the solvent melts the plastic) and can be filled cause you love to sand right? I have all the way down to .010 that I use as a shim.
Basic building techniques are much like wood. Butt end joints are weak weak. Invest in square, quarter round, solid, hollow etc rod of all sizes. Use is to strengthen from behind a joint. When you are shaping, you can sand through panels to reveal the "backer rod" actually becomes part of the visible part.
Don't forget my wife's favorite part...the snow from all the styrene sanding!
You sand for the basic shape you are trying to achieve and then you get to start filler and sand for days. Fun fun.
Buy some and start experimenting it isn't too expensive.