Look at what you need:
- One goalkeeper to replace Van der Sar after or during the first season
- One defender to replace Ferdinand after a season or so
- Perhaps an extra holding midfielder isn't a luxury, as right now you only have Hargreaves, who's injured and not so young anymore
- Depending on the way you're going to play some positions may need to be strengthened. Some extra quality on the flanks may come in handy, especially on the left. You don't really need strikers, unless you want to bring some height in the squad, which is missing upfront.
Once you figured out how many and what kind of players you need, look around, scout a bit, and make the transfers you think are right for the team.