1. It is true it's necessary search for a Exchange with the price cheap in BTC for buy it ?? That is a good recomendation for "Traders" and "Holders" too??
Exchanges will have the same prices because bots already work on the variance trading and they are really fast.
2. I will "holder" my BTC, I need buy in piece BTC or all my fiat money buy all BTC? What is the best strategy to be a good HODL in BTC?? And Why?
If you use all your fiat, then you will need to sell btc to get some cash again, so, i recommend to spend only the money that you will not use now, even you should see it as lost money.
3. What is your strategy for now in BTC? And why??
To hold is the strategy for yesterday, for today and for tomorrow.