Started a save as Benfica based of another thread discussion here. They seemed like an unstoppable machine with a near never-ending supply of talent. That said i'm only in Feb/March of my first season they're a very dominant team.
I only made signings to accommodate the sale of players, sold Eliseu for €2m and bought Adriano for €4m, sold Lisandro Lopes for €10m and bought Balanta for €7m and sadly Nelson Semedo wanted to leave so sold him for €22m (which i felt was low ) and took in Joao Cancelo on loan with an option to buy for €9m.
Apart from that they have loads of young players with decent potential who can cover any injuries along the way. I play with a 4-2-3-1 I have made myself which was very successful in a previous save but seems to really only suit Liverpool but also took a plug and play 4-4-2 from here but can't remember the name Midsummers something (it's only my backup tactic) and also have a 3-4-2-1 which was my main tactic from FM15.
They are a really fun team to be with the main challenge coming from Sporting and Porto and the real challenge would be a Champions League or 2. Hope this helps, Enjoy