The beginning of notable investment accumulation for many people starts once you get a job with a paycheck. With this type of employment, you may have the benefit of investing with your company sponsored 401K or Roth 401K plans, and if not, you can invest in a personal IRA or Roth IRA account.
The best rule of thumb to start out is to invest enough in your 401k plan to get the full match being offered by your company (if they offer a match). This is free money. Don’t turn it down.
If you’re on your own doing an IRA, invest as much as you can spare when you’re getting started, with the goal of hitting the yearly maximum.
With money in these accounts, you’ll have to choose where and how it is invested. Some companies may limit your options, but all should offer something that resembles a low cost Index Fund. This will give you good diversification while also keeping fees at a minimum.
For one of the best resources on Index Funds, read The Simple Path to Wealth