I started newly and I don't know which aircraft to buy
1) never buy an airplane in the beginning
2) depends on your concept for your company
3) you may want to watch available tutorials on youtube which help you to answer some questions
If I had more information about your airline I, and others, might be able to give some real advise about it. But for now I would suggest to take a look at the quantity produced for certain aircraft. That way you can get an idea for which aircraft are more profitable and which ones are more difficult to work with. It of course depends on what kind of routes you want to fly and if there are certain restriction (like short runways), but it should give a good general idea.
Emb 195s are always a nice starter aircraft for most newer players - Easy to get profitable, does most routes (bar really short runways) No route restrictions (except bar 10 to bar 10) and normally there are a few cheaper ones on the used the market.
Personally, I go for CRJ700's since it seems especially in more developed servers larger airlines return mid-life ones for dirt cheap leasing and you can easily make them pretty profitable depending on where you are located especially since you can have one pilot pool and have anything from the tiny CRJ200's to the relatively large CRJ 1000's.
Yes E95 is a nice plane to start with. Like the CR700 this plane is profitable even at the tab fare.
Have fun !