If you want to get better returns you need to take greater risk. Period. For most investors this means you follow the advice
Warren Buffett recently gave during his 2017 annual meeting: you need to own companies (stocks) and less bonds (especially long term bonds).
Owning companies is no panacea - their returns can be volatile and if you own only a few you have greater risk than owning many. That's right - diversification is the only "free lunch" in investing - generating the same expected returns while lowering risk. In addition, academic research on stock returns over the last quarter of a century has revealed three "risk factors" which generate higher returns for investors. University of Chicago professor Eugene Fama (a Nobel Laureate) and his research partner Ken French identified these signficant advantages
1) owning small companies vs. large