Which Cryptocurrency, I can buy in the current scenario?

bitcoin,etherium,cardano,bnb,solana,polkadot,polygon matic,

Don't have much time to explain why, but if you want to dubble your money in less than a week I suggest that tokens below:
FRZSS on Lbank = is in dip now and many fundamental news on the way
FRZW on Lbank = will list on CMC soon.
SHILL on any exchange = Has many reason to blow up the market.
AIOZ = Will get double less than a month.

Bitcoin < risk
Altcoins > risk

We're in a bear market, I'd DCA into bitcoin for now.

I'd say buy fractions of Bitcoin and keep stacking sats, if you want to buy some altcoin I'd suggest ETH, LTC, MATIC, AVAX or BNB. Stay away from Solana, if you spell it backwards you will find out that is Anal-OS, considering the Network Downtime that occurred in past months I'd not take it as a solid project.

As a final reminder, learn the difference between Proof-of-Work and Proof-of-Stake and you will have a more clear idea about what to buy!

Good luck!