You should have atleast 0.1BTC, if you have more you can choose more risky strategy and buy some altcoins. But remembery the most important thing is to have as most BTC as possible before halving.
You're right about buying as many Bitcoins as you can. At least we can all see that altcoins are weak in these matters. But, I disagree about the amount, this amount may change according to the average earnings. While the monthly salary in some countries is $10, some of these may be $10k. Therefore, the purchasing power may also vary according to the earnings.