I'm doing a Newcastle save too. First season I finished in a very, very average 11th place, second season I managed to win the PL. I did it with a lot of players that are at the club already. Ayoze Perez is a beast if given lots of game time, so is Siem De Jong. Anita and Sissoko can dominate almost any team in the middle of the park. Also, Yanga-Mbiwa and Ben Arfa coming back to you in the second season are like two free, top 4 standard new signings.
As for new signings, Stefan Reinartz was great for me. I bought him as a replacement DM for Tiote (I'd sell him for big money while you can if I were you) but Reinartz can also play CM and even CB well too. I got him for £3.8m. For the right attacking midfielder, my highest recommendation is Zaha, he's absolutely sensational on the game. I got him on loan at first but then bought him for £20m and he was so worth it. Got 14 goals and 19 assists as a Winger - Attack for me! I hope things go well for you!