Yeah jungle is a whole different beast then laning.
As far as your Lux game is concerned, it sounds like you are really good at laning. Obviously I haven't seen you play since you were like level 5 so my advice here is gonna be made from conjecture and not facts. So, you're winning your lane as Lux, your jungle is behind. Let's say your bot lane is a premade, they're mostly even and your top is behind but his opponent isn't fed. In this situation what you should do is this...
1. Get the blue buff
2. Leave your lane and tell your jungle to stay mid so they can soak xp
3. Gank for your losing lane
If that ends up with a kill for you or your top you should then do one of two things...
4A. Run mid and gank for your jungler who is mid and probably pushed against the tower or
4B. Recall, run bot lane, gank bottom and if that turns into a kill, you should ping your jungler to either immediately come for dragon (if its up) or you should push the bottom tower down.
Or you should...
5A. Push with your top and take the top tower
5B. Have your top come mid and the three of you take mid tower.
League of legends is a game of pressure. When you have an advantage, you have to leverage it across the map not just in your lane. If you're not currently doing something like this, then when you start doing it your win percentage will definitely climb.
If you gain a small lead in the mid but you can't convert anything, don't worry! You can't carry every single game. A way to expand your small mid lead though is to farm the rude dudes (now they're birds I guess) or the dogs in the jungle after you push your opponent to his tower. Lux can do this pretty quickly later on.