I want to show you (IMHO) the best strategy, that I am just using it. So here it is:
At first place we have to begin buy BTC at current price, and every price DUMP we have to used for buy more BTC. So we cant use the whole budget at first purchase. We have to split our budget, for more parts, where everybody else will be bigger (our goal is to achieve the best average purchase price). We have to determine possible prices for the entry of another part of the capital, the best zones for next entry are past supports and resistances.
E.g.:
purchase 10% of budget at current price 6680 USD
purchase 15% of budget at price 6000 USD
purchase 20% of budget at price 5000 USD
purchase 25% of budget at price 3000 USD
purchase 30% of budget at price 1800 USD
You can tell me, that price 1800 USD per BTC is impossible, but at the crypto world is nothing impossible and is better to be prepare for all possibilities. And with this strategy you have some BTC at every moment, I dont think that not to be ALL IN is problem (better lower profit, than big loss).
Some tips:
Never sell under your average purchase price (either wait, or buy more BTC, or multiple BTC through the altcoins, you can see, that when is BTC going down Altcoins are faster and when is going up they are faster too, you can used it, but again, not ALL IN, you can use this strategy too).
Dont use small altcoin markets when are pumping for multiply BTC - there are Pump and DUMP groups.
Dont buy shitcoins for multiply BTC, try to choose strong old Altcoins with big marketcap.
And the most important is to have Coins at safe! Dont be thrifty and buy Trezor, Ledger or something else HW.