ok mates thanks for everyone for precious comments. After reading all your comments I decided to buy a used bike for start and this is what I bought. (Can't post the url until 10 posts I will add later)

Giant Defy Advanced 1 (2015) $1245
Ultegra 6800 shifts
TRP mechanical disc system
Giand P-R2 disc wheel set
Weighted 9,2 kg

I had a short run and here are my first impressions:

-It won't be that easy to achieve 30 miles a day as you guys just said I was exhausted at 7th mile. Hopefully I won't need more then 2 months.
-Didn't like the mechanical disc brakes, already want to upgrade them. (Bike shop guy said I can sell TRP brakes for around $150 does it seem correct?)
-Bike shop guy also said a wheel set would be a big upgrade. He recommended Campagnolo Zonda for value.
-The frame is di2 compatible.

So as far as I understand a hydraulic disc set and upper mid level wheel set will take the bike down to 8,5 kg which I'd like. But I'm not rushing for now. I will get used to the bike until I will be able to tell the difference after upgrade.