What does the team need? Start with what they don't need. Tatum, Brown, and White have swing (SF/PF hybrid), wing, and guard covered. Pretty much everything else could be considered a need to some extent. If the bench was Pritchard, Hauser, and Queta, plus some mix of Walsh, Scheierman, Gonzalez, and so on, I would say the bench is solid also. I could see Vucevic as a very solid bench player also. But who are the other two starters?
I see the ideal 4th and 5th starters as a ball handling guard and a center (fairly obvious, most everyone is saying the same thing to some extent). Pritchard could be the starting guard, but he seems best suited as 6th man. Queta could start (again) but you would ideally like a little more offense out of your starting center. Problem I see is that I don't think both of these holes can be filled and stay under the tax.
That is why I see the path as sign a good solid starting guard via FA. There are some options out there. I like CJ McCollum but others have said he is likely staying in ATL. We are talking about a 4th starter level guard (McCollum is probably better than a 4th starter). If you do that, there is probably not enough money left for a starting center and there aren't any great options at center anyway.