Attack: Marcus Rashford, Romelu Lukaku, and Douglas Costa

Marcus Rashford has been sensational under Solskjaer and the youngster will be a confirmed starter for Manchester United in the coming weeks. His pace, counter-attacking ability, and natural attacking instinct have borne well with the squad and resulted in a number of goals. He could emerge as United's main man in the coming years.
Although Romelu Lukaku has looked off his mark this season, the Belgian is a load of talent to ignore. As seen in the World Cup, Lukaku is capable of creating chances from the midfield as a striker apart from scoring his usual goals. With his physicality, he would be an advantage for the squad and hence, Lukaku would be a preferred squad member for the upcoming season.
United has used Juan Mata and Jesse Lingard at the right-wing position and both are yet to seal their place at that position. Hence, United should look for a genuine right-winger and Juventus man Douglas Costa could be a suitable option. The Brazilian has suffered a lack of game time this season and could move this summer. His pace and creativity would be an advantage for the United squad and therefore should make it to the United XI next season.