What type should I go with for 6th Pokemon? Also is that a good team setup?

I have

Fire/Psychic
Grass
Water
Dark/Steel
Poison/Fighting


Anyone have any ideas on 6th type?
Also is this a good team setup?

2016-03-23T12:43:20Z

@ Aden- why would I do that I have fire/psychic and a dark/steel. So why would I want to do that. That would be stupid as having more than one of the same type is dumb.

Theodoros2016-03-23T13:28:23Z

Normal tank

?2016-03-23T12:40:07Z

Dark/Pshychic.