~te ikimasu and ~ni ikimasu

You're confusing when to use ~て 行きます and ~に行きます ???

In english, “~te ikimasu” & “~ni ikimasu” is very much the same but in Japanese, they were different. “~te ikimasu” represents “doing something and go” where “~ni ikimasu” represents “go and do something”

Example
Kudamono o (kau)katte ikimasu - I will buy fruits to your place
Kudamono o (kau)kai ni ikimasu - I go and buy fruits

~ni ikimasu is a combination of the following scenario
Go to post office - Yuubinkyoku e ikimasu
Buy stamps - Kitte o kaimasu
I go and buy stamps at the post office - Yuubinkyoku e kitte o kai ni ikimasu
Meaning : Kitte (Stamps)

Other Examples
I go and play at friend’s house - Tomodachi no uchi e (asobu)asobi ni ikimasu
Who would you go and meet - Dare ni (au)ai ni ikimasu ka
Meaning : Tomodachi (Friend), Asobu (Play / Visit), Dare (Who), Au (Meet)

Well, in English we normally don’t use “go and” but just “Who would you meet”.
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The other day I shown you the usage of “~te kimasu” which mean “doing something and come back”. Today I will cover the opposite way - “Go and do something” (~te ikimasu).

Example
Go out from home - Uchi o (deru)demasu
Buy cake - Ke-ki o (kau)kaimasu
Go to friend’s house - Tomodachi no uchi e (iku)ikimasu
(I will) buy cake and go (to friend’s house)- Ke-ki o katte ikimasu

You only need to mention the purpose. In the above example, the purpose is to buy cake to a friend’s house. So you only need to mention that you are going out to buy cake.

Other examples
I go and put the luggage in the room - Heya ni nimotsu o (oku)oite ikimasu
I go and send letter at the post office - Yuubinkyoku de tegami o (dasu)dashite ikimasu
I go shopping at the department store in front of the station - Eki mae no depa-to de kaimono o (suru)shite ikimasu
Meaning : Heya (Room), Nimotsu (Luggage), Oku (Put), Yuubinkyoku (Post Office), Dasu (Send), Kaimono (Shopping)

Another usage - Doing something and go
I will take a train and go - Densha ni (noru)notte ikimasu
I will bring camera and go - Kamera o (motsu)motte ikimasu
I will wear coat and go - Ko-to o (kiru)kite ikimasu
Meaning : Densha (Train), Noru (Board - for transport), Kamera (Camera), Motsu (Bring), Ko-to (Coat), Kiru (Wear)

Hope it is not too confuse.

Source: http://nihongo.anthonet.com