I would say on this bike you can install any cheapest aluminum crankset, cheapest front derailleur and a friction (non indexed) shifter, where the crankset will be the most costly part (about 30$) and a few dollars for derailleur and shifter (each). So if you able to do the work byself you will end under 50$ for all that upgrade (but those should be done well), however if you want LBS to do the work it should cost about 20-30$ more (I don't really know the work costs in other than my regions).
As Batman mention in the comment, your BB can be too short for triple crank. If it is, the upgrade can't be done without replacing the BB too.
I didn't include tools cost in my answer.
And to get this work done you have to have appropriate knowledge.
As bikes have different width seat tube, your derailleur must fit it. If your frame tube is thin (and it looks that this frame has thin tube) you can take a little wider derailleur and put a holder plates between it and the frame. Of course you should check that the derailleur will be compatible to your crank teeth count.
It may seem difficult, but in LBS will be done easily. But you should compare it's cost, and cost of a new bike of same quality with front gears.