Okay, I'm going to play FM but I'll try to be realistic. Forget Verrati, Hazard, Griezmann and even Mbappé who should prefer Real.
With 300M to spend (222 + 80 of the remaining budget of 2017) would try 3/4 players.
To the place of Neymar i choose Dembélé. He has all the qualities of Neymar. Finishing, technique, decision making, passing, crossing and game vision. In some of these areas he´s not so good but it's still 20 years old. He's the closest to Neymar I know. 80M thus shooting into the air.
Then to the midfield I choose two players: Coutinho or Eriksen for Offensive Medium and then someone much cheaper but that in my opinion undervalued: Seri. You can laugh at ease, but Seri is not as far behind Verrati as you might think. 40M in Seri, 100M in the Coutinho or 80 in the Eriksen. I do not think it's lunatic.
The 4th would be Insigne. Last season he showed everything we already knew: amazing on the two wings but was irregular and inconsistent. Last season he was not. He was very regular and along with Mertens ihe was great in 90% of the games. Napoles sells expensive, I know. 70M.
Well: Coutinho, Seri, Dembelé, Insigne makes about 300M.
I would sell 3 players of this lot (Rafinha, Gomes, Arda, Denis Suarez, Samper, Munir, Vermaelen). Arda and Vermalen upfront. And with this extra $ try an extra central defender because I think Marlon is still green and Mascherano is not going to get any younger.
Stegen-Cilessen
Semedo / Vidal Pique / Marlon /? Umtiti / Masche Alba / Digne
Busquets / Samper / Gomes
Rakitic / Seri / Gomes Iniesta / Coutinho (Eriksen) / Denis Suarez
Messi / Rafinha / Insigne Suarez / Alcacer / Munir Dembele / Insigne / Coutinho
PS: Robert will fuck this up.