My suggestion as a new player not too long ago is - take it easy.
Don't worry about power-levelling or creating the most powerful character: you will have plenty of time to figure that out at Admiral ranks.
The first 40 levels of the game are meant to gradually familiarize you with STO character and ship design, and how to make all of them work for you (you are entitled to find your own style).
Unlike what others may say, at this stage you're welcome to try anything you want. Min-maxing is something that ruins the fun because you're told to follow certain (obscure) rules and fly "someone elses" ship.
It's much better advice for you to take your time with the missions, progress from the starting light cruiser to something that resembles, with time, a 25th century warship... and then that's the time to explore player to player competition, elite fleet missions, etc.
All in good time.
The best pilots I have in my guild are not the **** hot fighter pilots, but the ones who took their time with the game and enjoyed every moment of it.
They bring a unique blend of Star Trek canon-ness with them to Admiral endgame play and do not hesitate to lend a helping hand to other new players in need.
And that's the sort of Starfleet Captain we all hope to see. This game ain't just about blowing stuff up, once you get past the initial confusion stage
For me it's a game of endless experimentation, adaptation, mutual support for those in need, and something very seldom practised in the gaming world today: -
Player development through veterans' coaching. Starfleet exists to train and develop the next generation of officers for future command postings, and this very forum is the perfect resource. Again, don't rush to ask questions (you might get a million suggestions on obscure "sure win" strategies... which are not needed at a mere Lieutenant rank!), and read as much as you can to know the best practises and who/what to avoid in a pinch.
STF Flight Instructor since Early 2012. Newbies are the reason why STO lives and breathes today. Do not discriminate.