Hey I need help with building my team

Is this for Arena? if yes then replace Xander for hardin(Xander is good but he scores so low that he will heavily weigh down the team, and Hardin is armored so he is good overall and scores high). If not then ok.

What do you have in mind for the team and what role do you want each unit to have, I can only guess that L!Marth is for Dragons and/or you frontliner, Lancina is support(cause of her weapon), Celica is a sweeper,and Xander is the refresher.
with the team in mind then i can only suggest is to fill the holes, give all of them a seal that will help them in their respective roles.

Your team is fine for clearing content. Maybe try running WTharja, Hardin or Fjorm if you need a tankier unit than marth and lancina.

For arena... Your Hardin is +Atk/-Res. He will score very well in the arena. Give him Warding Breath and the QR3 seal. Don't fodder your only Like, though. Wait until he comes up again on a legendary banner and try to pull one. It would also be a good idea to save orbs to try to pull more Hardins and more Fjorms. Hardin is a top units in both effectiveness and arena scoring. Fjorm is a good well rounded unit that is a frequent arena bonus unit.