Question

I suggest you to become an engineer....is it mandatory to use " suggest + to " ?

Answer 1

it is not mandatory. you can also use
i suggest you become an engineer

Answer 2

Well it is not mandatory but it willbe best to use it.

you cant write- I suggest you become an engineer.

it does not make sense.

You can write - I suggest you, become an engineer.

it is best to write "I suggest you to become an engineer.