hi and welcome , i found doing a lot of homework i.e :- reading as many books and practising knots , worked for me as well as the field work ( out fishing ) , and remember never be afraid to ask , good luck :thumbs:
Im also a junior angler aswell, Im 15 years old. Personally the main two things that have improved my sea fishing are, 1: Find a mark that produces well and stick to that mark and find out how it fishes I.E what state of the tide is best and wind dircetion. I reguallary fish dungeness and I have found it fishes best at low water because there is very deep water 100yds out also, I have found it fishes best after a SW blow. Secondly I would say my catch results have improved loads by learning to cast far, on the field I can hit 150yds so on a good day I can put a bait out 120yds and even when its quite windy I can still hit that 100yd mark with bait. You don't need to be big built either to cast far I'm just an average sized 15 year old. Heres a number for the sea angler office and they will put you in touch with your nearest instructor 01733465759. Also a casting instrucor is much better then learning from videos. As for rigs and that just keep it simple.
Fish where you can cast into the fish feeding areas. If everybody is goign to a mark where you need 100 yards or more cast to catch and you can't cast that far then dont bother fishing there.
When fishing split the area in front of you into 9 boxes in a 3x3 shape and fish each small box until you catch then keep on casting into that area
Get out there and fish the crap out of everything! Get loads of experience as soon as possible and like rayking said never be afraid to ask.
I'm new to fishing and I've learnt (what I hope is) loads from fishing with different people and trying different things. It follows the same format as everything in life:- the more experience you get of different things, the more you can take into your next experience.