An E-Power kit can get you into regulated 3.7v vaping for under $50 and it will include a couple of batteries and a charger. These should run the dualies safely. You might want to pick up an extra battery if you plan to do the dualies...they can take down batteries nearly twice as fast as regular cartos.
You can also find plenty of box mods and rough/simple tube mods for under $50, but getting good batteries and a charger for them will usually drive it up to more like $80. If you're thinking of going this route, consider getting something big enough to take at least an 18650 sized battery...then you get options to stack different batteries for 5v or 6v vaping.
Welcome to MadVapes LLC has the E-Power, a good selection of inexpensive mods, and they also carry IMR High Drain and many other types of batteries..
Also give this site a look:
Best e-Cig Mod List | e-Cig Mods Database