Try reading JL Collin's Stock Series.
http://jlcollinsnh.com/stock-series/Basically, try to buy low cost indexes and avoid fees.
If you're just starting, I think it wouldn't be unreasonable to just dump it all in a low cost SP500 or total market index fund. As your stash grows, you might then think about more diversification (total bond fund and total international index).
MVal: I would avoid whatever the fee you are being charged for someone else to do your asset allocation. If you're 100% US equities (SP500 or total market), there is no rebalancing. No rebalance necessary in target date funds either (they do that in the fund itself). If you have something like a three fund portfolio (US Stock Market, US Bonds, International Stock Market), you need to (1) pick an asset allocation [% you invest in each of the three funds] and (2) rebalance once a year [reset whatever your current asset allocation is to your desired allocation in (1)]. Once you've figured out how to rebalance once, it will probably take you 10-15 minutes a year.
Re: Picking an asset allocation.
Lost of people will advocate for 100% stocks. This may be a good decision if you can handle not selling when the market drops.
Personally, I keep my bond allocation between 15-20%. That way, I can rebalance when the market drops a bunch and I feel like I'm doing something.
Also, I think that keeping a small amount of bonds will limit the downside risk (likely at the cost of reducing the maximum possible return). I think this because of work that has been done on safe withdrawal rates that show that success rates were higher at 75% US stocks (25% bonds) than at 100% US Stocks. While it's not quite the same (because we're accumulating instead of withdrawing), I think that it's probably not unreasonable.
https://earlyretirementnow.com/2016/12/07/the-ultimate-guide-to-safe-withdrawal-rates-part-1-intro/Re: poor fund options. Remember that you don't need to have all 3 funds (in a 3 fund portfolio) in the 401k. Some could be in Roth IRA or tIRA, some could be in taxable. For example, if you want international and all the international funds in your 401k suck, hold that in an IRA at Vanguard. If the funds in your 401k suck, contribute to whatever match you have then max out IRA / HSA options, then go back to 401k.