Newbie: issues withDevo 10 / 450 quad set up

I have searched - believe me I have spent hours on this and other forums and youTube.
I have sat with the KK2 manual and the Deviation Manual side by side and gone through them.

I have a self build 450 size frame X quad.
Mars Motors 2212 980kv
ZTW Spyder Oneshot 125 small Opto ESCs
HobbyWing uBec
KK2.1.5 flight controller
First check flight - hovered more or less stable but moved back towards me - and right ( as seen) rather than "drifted". Went through KK2 going through the PI editor - receiver test etc,. Seemed to make it worse and its flips over before it can make 2 feet high.
Went on youTube found a newbie ( sadly 2012 video) with a 450 quad X frame build as used his KK2 settings - his flew nice and stable - mine want to be a lawn mower - and flips still.
Today I download one of Tom Zs quad ini files which is now on my Devo 10 - went into the garden with everything crossed - its still a flippin lawn mower.
I have gone through the... it's something simple I have missed - its something stupid I have done - its the wife's fault routine - every setting in the KK2 and Devo 10 seems OK... but they would to me!
Although the settiing and sticks say otherwise... its as if its set to turn right withe the throttle/pitch and rudder acting as one.
I have held it by the landing legs and just used throttle - its pulls to the right - if I tip it back left... the motors speed up to push it right!
Would appreciate and suggestions - although I have convinced myself that this Devo 10 was returned as faulty before it was sent out to me -and maybe its a flawed product in some way.

( Is this normal for newbies - or am I just brain dead?)

The usual missed step in a first time set up is missing the tx calibration step. Use the transmitter menu calibration entry, and follow the directions on the pages it pours up.

Of course, if it's your first build, it could be something off in the build. Just some part off center or off kilter or loose or who knows what else. Best bet is to get someone who's dinner successful builds to look at it. Failing that, but a cheap BNF or RTF quad and see if you can get it working.

+1 to calibration. This seems to be common with RTF and BNF quads, too.

Also, check the rotation of your blades... In fact, I do all my TX/FC calibrations with the blades removed. If your blades are on the wrong motors you'll also get weird results, so I prefer to eliminate that issue. When it's roughly right, e.g. the TX throttle increases all motors, the TX pitch forward increases the back motors, TX roll left increases the right motors, etc., then put on the blades for field calibration.

The Mars motors I have were a boxed set.. 2 cw 2 ccw with threaded shafts. I used DJI cloned props with metal screwed hubs. and also checked the spin direction during the CC3D setup - so I am happy that aspect is ruled out.
I was about to strip the 450 frame of all the electronics today and replace everything with:
Genuine DJI motors - emax 30a Simon series ESC - CC3D Atom - when I noticed that all the arms were sagging just a little - but enough to show 1 to .5 bubble shift in a spirit level. So this in effect had the motors pointing outwards. The Phantom P3 motors and a slight tilt inwards and I see on eBay somebody selling "wedges" which will tilt the motors - so maybe the sag in the arms adds to any other negatives.
Will be adding some heat later to see if I can get a little correction in the arms. Hoping to have the rebuild completed tomorrow, so will get back with any news.

Thanks for replies and suggestions

Sounds about right!
I did everything in the KK2.1.5 setup except the TX settings. I went into the Devo and tried to set ail, ele rud throttle to "0" then went into the Pi editor and corrected again.
Thanks for the reply and advice