Hi Kano! This IS an exciting spring-y moment.

Just a word on the components:

I would speak against getting lower-end components now and upgrading later. In my experience, it's much more expensive to buy individual parts than to get the whole groupo when you get a new bike. And you want your riding experience to be satisfying, not frustrating.

I haven't personally have had to deal with Sora or Tiagra but what I've seen on the bikes of others has made me glad I haven't. They "work" but require a lot of adjustment and you never know if they will stay adjusted or when they will become misadjusted. Perhaps the owners of the bikes I've seen so equipped have just not been lucky. I also know that I'm very fussy about gearing: when I click it has to shift, period. (I ride hills a lot.) But I found even the brakes on Sora to be not-so-reliable in their adjustement.

If you can afford it, do get as much 105 as you can or even Ultegra.

Something you can perhaps more easily upgrade in the future is wheels.

And regarding your pedals: if you're used to clipless, then put them on right away. No doubt about that.

Enjoy!