I recommend invest with small amount like 20% of total the money you have, i thought that make you feel comfortable than you invest your money in huge amount, targeted coin on Top 1-50 and after you bought coin you should have a target for profit what you want around 5%-10% or more. Don't be greedy if you have been profit, out of the market at right time before going down, especially never do cut loss if you want don't loss your money due to we never know of market situation at this phase bear market
I am not a fan of lump sum investing. It could be beneficial but the risk to lose is high. Dollar-cost averaging (DCA) remains my best strategy because it spreads the risk and is more comfortable to invest gradually.
No matter what the current price is, people always think there will be better opportunities to either buy or sell. It's a vicious circle. I am not sure why you believe the price will drop to $20-25k. If the value drops to $25k, you will be waiting for $20k. If it drops to $20k, you might think it's better to wait until $15k. Too much waiting, and you'll miss the train. If you have money to invest and you are willing to do it, go ahead. It's the same when you are selling. If you have made some profits that you are satisfied with, dump your bags and get back in the game with the next cycle.
I totally accept your position @Pmalek because if one keeps waiting for bitcoin price to fall to their expectation, it might never happen. I know so many persons that are regretting their indecision which has made them miss an uncommon privilege to invest in bitcoin. The price of Bitcoin might never drop in the nearest future, who knows? It is risky not to take risks, so it is better to buy when you have the opportunity. We shouldn't also be greedy because we may also lose out. Once it has gotten to our target (not too high) there is a need to sell and make some profit. After that, we can start another investment project.