I started the game around early June last year. I hit max rank this morning.
Some simple advice I could give is to try to complete all Daily Activities + claim your Daily Calendar stuff for momentum. Avoid spending Crystals on characters in Shipments unless you absolutely need to unlock them, or they are really difficult characters to get (example: ships that can only be farmed from Hard Nodes such as Rebel Y-Wing, Jyn Erso, and characters that could give good early-game boosts in some Journey Guides but have unlock area that are difficult to obtain). Best place to spend Crystals would be for packs (always buy in bulk) and Bonus Energy.
For the best early-game boost, you can try to invest in a Phoenix Squad, though the best setup (Hera, Kanan, Chopper, Ezra, Zeb) might not be achievable until Level 40. Phoenix Squad is generally difficult to deal with in the early game, as I doubt lower leveled players would have access to characters who could shut it down easily (Darth Traya, Boba Fett, Jango Fett, Count Dooku with maxed out basic, characters who can spam buff and healing immunity en masse, etc), in addition to being useful for Emperor's Demise and Artist of War Journey Guide events.
When you unlock Squad Arena, try to invest in Windu, Tarkin, and Ackbar for slight boost in Fleet Battles. Since Cantina Battles doesn't have a battle limit, you can try using Sim tickets ("use them sparingly, for they are rare") on the node that provides Unmasked Kylo Ren Shards, as it also provides Tie Silencer Blueprints, which can stack up offense when attacked or if it hits a target locked enemy, which can work well for the three starter Fleet Commanders: Windu can cause target locks and force enemy units to attack Tie Silencer; Tarkin's reinforcement bonus gives retribution, meaning that Tie Silencer can get double boosts if counterattacking a target locked enemy; Ackbar can heal and grant bonus attacks. (Added bonus: it can be unlocked at one star.)
Hope this all helps, and good luck on your journey!