a team usually consists of a Tank, a DD, a Healer and a subDD. you want to build them purely from one type, hybrid is bad here. some supports are an exception to that though.

Miri is a solid DD for most situation, she doesn't top any charts but she can do well anywhere. you could someone else too, but why do so when you already have someone useful.

you have a few options for the others. You will get a 5* ticket eventually, so you have 2 more heroes to pick.

Frey is good for a healer with her recent buffs i dont see a huge reason to get the usual recommendation (rephy or laias) from those ticklets. you can do so if you want, those 3 are quite good. only priest i'd consider buying as a beginner would be medi.

for a tank, there is only one good option for beginners in the starter tickets and thats jane. she is really good for general content. you could buy someone with the rubies. nera being the most notible as a defensive tank janes offensive utility.