There are different opinions about it. Some people say that the best source is trading, others point out the lenging business as a better alternative, and there are people who recommend some icos. I think at the moment it is risky to invest in icos. In trading and lending business there is potential, but the risk is also high atm. So, I would probably hold Bitcoin, and wait until better times to invest.
All of the three that you said, trading, lending, and investing in ICOs are all risky at the moment and will always be risky. There's no time in a day that it becomes less risky. Now that you're aware of all the risks that you're going to be taking, you should decide if you're brave enough to take those risks. Remember that high risk = high returns.
Personally, I would only do trading and participating in ICOs. Participating in ICO doesn't have risk at all since you just need to use your twitter and/or facebook account to get a share/stake. Just don't sell all of your coins right when you received the bounty rewards because the coin might go higher than you expected.