New player with 10 years experience

Hi everybody

So I am in a bit of a weird position. I have played swgoh for 10 years on and of (mostly on), but played simply as a star wars fan who thougth it was really cool to just gather all my favorite characters from the movies. I now want to take the game a little more seriously and have hit a bit of a problem. Because I have done free to play for so long I have 6.3 GP and even a master Luke Skywalker, but no clue about optimal mods, good and bad squads, datacrons and all that. Looking through beginner guides is somewhat helpful but I have found that a lot of the things they say to do simply does not apply to me because a lot of my characters are already high level. When I than look into hints for higher levels I get confused by slang and abreviations and what feels like a 1000 different things that i need to consider. 

So therefore I want to know if anyone has any really good tips for me or somewhere where I can read about explanations for "high level" players that does not assume i have been in the game for a long time.

ps. I migth be willing to starts using a little bit of money, but in general i don't like the gambling of buying loot boxes where you migth not get anything good and because of the grind most of the beginner friendly packs give me characters I already have. If you know of good things to buy that does not cost more than like 30-50 dollars that would also be great.