The existing portfolios focus on low-cost exchange-traded funds that offer you diverse investments without a giant starting investment. Stash is an excellent choice for a starting point. By Eric Rosenberg. You can invest in a portion of a share instead with a much lower minimum investment. The Acorns app is a great choice for first-time investors. We may receive commissions from purchases made after visiting links within our content. Investing in the stock market for the first time is intimidating, but it doesn’t have to be.