Investing with Robo-Advisors is sufficient but honestly, it's not optimal as these advisors will place your money into funds and charge a high platform and fund fee to do this.
You can do this yourself with very little thought, expertise or time and save yourself money.
Here are the steps:
1. Take one or two hours to research your risk tolerance and make sure you understand thee basics.
2. Sign up to an investing platform like Vanguard or Hargreaves Landsdown (booth Koody and my website review these I believe)
3. Find a fund within these platforms to invest in that matches your risk tolerance with as low a fund fee as possible (below 0.2% is good) which tracks an index such as global shares or the S&P 500.
4. Set up an investing instruction for either a lump sum or a set monthly amount to invest in this fund.
5. Within the platform, set up a direct-debt to fund this monthly investment.
As should be clear, after the initial research and sign-up phase - this strategy takes basically 0 time other than occasionally checking your investments.
Taking a day to do some research and get set-up is WELL WORTH the money you would save by not using a robo-advisor like Nutmeg in my opinion.
If you're really clueless on where to start - services like Nutmeg are a lot better than not investing at all or speculating in individual company shares
Hope this helps.