Wukong mid is pretty fun. I can rarely play him in the top lane (bad matchups against many tanks and bruisers) and I prefer junglers who have better clears, CC, and durability; however, I love playing him mid lane. Wukong's mid lane matchups are generally pretty easy since most of his opponents will be squishy, many will be immobile, and many rely on skillshots for damage (which can be dodged or blocked with W). He can also roam well from mid lane, taking advantage of his powerful ganks to snowball other lanes. Just be careful about picking into something like Lissandra or Annie.
I've never really played Kha'zix; I've always found him too feast-or-famine for my liking. If you can make him work he's fine, but I find that Wukong is generally a safer pick since he provides more utility (armor reduction, AoE knockup) when behind and is still useful when built tanky and you don't need your target to be isolated.
I wouldn't really recommend using control junglers too much in low elo. Many of them rely on coordination with their teammates to properly take objectives or teamfight. I would recommend using more damage or gank-oriented junglers, since many of them also provide good objective control and/or teamfighting ability. Vi, Gragas, and Fiddlesticks are all very strong picks and game-changers when used well.
Fiddlesticks can be especially terrifying in low elo since he can easily solo dragon, many players don't ward appropriately so you can easily gank, and you provide massive damage and utility. He can be a bit odd to learn since he plays differently than many champions, but he is very rewarding to know.
Amumu is generally a solid pick; good damage, clearing, durability, ganks, and teamfighting ability. The only thing he really lacks is early dueling potential and mana sustain.
Also, this cannot be emphasized enough. Always, always, always ward.
Wards let you tell where the opponents are, letting your team escape ganks and picking off enemy players or letting you know when it's safe to take objectives or teamfight (i.e. you see the enemy team is missing players and you have a number advantage).
One thing I always try to do is upgrade my Trinket at level 9 (or ASAP if I need to finish a big item and don't have enough left over). It's only 250G for either one free ward per minute or the ability to ensure an entire area is clear of wards. Using these you can easily secure objectives or provide massive amounts of vision (I'll pretty much always have 2-3 wards down on the map).