Do you think that if i buy "x" amount of BTC for any price below $10,000 USD will get me a profit on a long term (>1 year)?
Yes definitely.
If you just started and set certain amount to invest in bitcoin, use 50% of your investment fund to buy now at $9k
then buy more when the price drops, use 10% at $8k, use 15% at $7k, use 25% at $6k
when it goes up to $12k+ you can sell 10% of your bitcoin every $1k price increase or hodl for >1 year like you wanted
or simply just spend all your investment fund at your targeted price and sell 1 year later
if you currently already invested some, you can do something like
but you can
"somewhat" take the advantage (and risk) of current downtrend price
by doing tweaked DCA, buying at $9k (10%), at $8k (20%), at $7k (30%), and $6k (40%) if you believe $6k will be the bottom level
the % is the % of total fund you are willing to put into bitcoin

do it at your own risk and discretion