If you want to approximate something like a total market index (such as VTSAX), buy the large cap, mid cap, and small cap funds in an 80/10/10 ratio.
Even with fees as high as your plan has, the tax savings on the 401(k) are usually worthwhile, especially if you don't plan to remain in the same job for a decade or more. However if you can't afford to max out both your 401(k) and an IRA (and an HSA, if you have a qualifying health plan), start with 401(k) up to the match, then HSA, then IRA, then finally go with 401(k) contributions past the match.