Flash decisions?

Hey everyone 

I mainly shoot landscape but lately I have been trying to get into photographing kids outside and what not.... Light isn't always the best when shooting and sometimes parents want shooting sessions during harsh light... I feel like a flash can help balancing the light or filling in... I own a D750 and will be buying a Tamron 70-200 f2.8... 

What flash can I start with? Something that won't break the bank but also will give me options if I need them?

Please Help.

Thanks !

I didn't find the right solution from the internet.

References:

- http://www.thephotoforum.com/threads/flash-decisions.4187249846512

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