The issue is that whether you want it or not you will feel good for him when the coin goes up, but the opposite is also true and you feel bad for him and somehow guilty when the coin goes significantly down. I have always refrained from giving a clear recommendation to buy and I did well with it. You can still phrase a recommendation in a way such that you don't really tell him to buy, but wouldn't tell him not to buy might be a better way to put it.
Usually, good friendships are above a recommendation even if it goes wrong because both parties knew that it could happen, but some will be mad at you certainly.
To avoid that to happen it's always better to give them pointers to review before letting them to pursue their own careers inside this market.
Recommendation always inside us as we wanted our friends or love ones enjoy those benefits that we are having from this industry.
But the difference is we all understand the risk, and that what you have to introduced to them before anything else, letting them understand that there's always a high risk that they needed to surpass in order for them to enjoy and succeed from this venue of investment.