Magnet is something I believe should be saved for later on AFTER you have your fundamentals down. It's not exactly the most intuitive tool and takes a lot of practice and finesse to get down IMO.
As for your wavebouncing question, allow me to direct you here:
http://smashboards.com/threads/turnaround-bs-b-reverses-and-wavebounces-know-the-difference.334389/
For wavedashing out of DJC, I jump with y + tap (I angle the tap diagonally so I get the either the forward or backward swing with the DJ) and then roll the stick down and press L for the WD. Again, this is something I wouldn't work on until your fundamentals and tech skill are very solid.
For wavedashing out of Magnet, you might be referring to "Magnet dashing." You do this by short hopping and then magnetting as close to the ground as possible, and then jumping and wavelanding out immediately after. This is a situational technique, but is very good for baiting and comboing floaties at higher %. Mag dash also forces a knockdown/tech on spacies at higher % as well.
If you'd like I can provide footage of me doing all these things when I get home.