Re: bought a 308 today
My suggestion will be that with the FGMM, choosing between the 168 and the 175 will not be as much about which is more accurate than about how far are you shooting. If you're actually shooting beyond 800yd, the 175 will be the better choice. For most other brands, this advice will probably also apply.
The EGW is an outstanding choice, but for future reference, it's at its best under exceptionally rough handling. Lesser components will work well enough for those of us who don't have to live a rough and tumble shooting lifestyle.
If you don't handload, start as soon as is practical.
If you don't have a 22 trainer, you'e missing out on an opportunity to do the bulk of the marksmanship improvement grunt work on a platform that favors the obligatory repetition in a more pleasant and affordable manner.
Great optics are great optics, but if their cost and your wallet dictate that their acquisition seriously delays your entry into serious shooting, it may pay to consider an intermediate set of optics. That intermediate scope will still have a home as an upgrade on your trainer.
Finally, nobody gets really good at this stuff on their own. Find folks who already do this pretty well and enjoy their company.
Greg