first of all you're young and have a long time to grow into your body...you definitely need to be taking in high protein, moderate carbs, and moderate healthy fats...at your age I wouldn't take too many supplements or shakes, you need to be getting 95+% of your nutrition from real food, honestly anybody should be doing this, but for somebody that is in the prime of puberty this is a key to your success in the long run, imo
you are possibly overtraining by going to the gym 5-6 times per week and you've only been doing it for around a month, which is not a long time to have been working out anyway, it takes time for growth to occur, it doesn't happen overnight...I would probably cut back weight training to 3 sessions per week at 45min-1hr of actual lifting time per session...you should concentrate on big compound movements like bench press (chest), military press (shoulders), squats (legs/back), deadlifts (legs/back), just to name a few, you can do a google search to find a whole bunch more if you don't like the ones I listed, but those are the best and most common compound movements...don't do squats and deadlifts on the same day as they both stress your Central Nervous System immensely...if you want to work your biceps and triceps do barbell curls for biceps and close grip bench press for triceps...
one thing to remember is that while you are working out you are breaking down your muscles, so you have to give them ample time to recover because recovery is when growth actually occurs you also have to give your CNS time to recover and the only thing does that is time...also playing rugby I would assume you do a good bit of cardio and this can inhibit muscle growth to a degree as well, so I wouldn't advise doing any cardio outside of your rugby training...stick with the weight training and be as consistent with your workouts as you can and believe me you will begin to see progress, it just takes some time
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