I try to buy Bitcoin now because is a period of my life that I can invest 300-400$ per month do you think that Btc is a good investment option for me and the range of the money I can invest monthly ?
$300-400 per month would be a very good investment if you can afford it. But since crypto investment is very risky, you must have the ability to lose those dollars. But currently, since the price of other coins, including Bitcoin, has already gone up a lot, investing in the market will be much more risky now. So again wait for bear market and from that time every month you can invest such amount in bitcoins and other potential coins. In that case it will follow the DCA method and you will get a good savings after a long period of time as well as a huge profit.
Since the OP said he or she already has those $300-$400 ready to be invested, it's a clear indication that it's what he could afford to risk if you ask me, so if the money is readily available and it's set out for investment purposes, I don't think there is any need for me to give the person advice to take a break and wait for the bear market;
I would rather advise the person to DCA; sometimes he will be lucky to buy at a high price; other times he might also be lucky to buy low; it's just a matter of being consistent if the spare money is there, because the market can't actually be predicted very well; it doesn't always work the way we plan it.