February was something of a lean month for cryptocurrency investors. Many currencies – from well-established coins to brand-new upstarts – performed poorly, with some depreciating in value by over 52%. Virtually every single coin was down last month. Of course, like any other market, crypto has its highs and its lows – and with plenty of rumoured collaborations, new technology implementation and big-business partnerships, there are plenty of digital currencies which look like quite an attractive proposition for investors in March. Without further ado, we’ll consider the three best cryptocurrencies to invest in this month:Polymath (POLY) is currently sitting at a value of $1.04 and has a market cap of just under $250 million. Having launched at the beginning of February this year – a notoriously bad time for crypto all-round – it has defied the odds, increased in value and held its own, even during a market downturn. Dubbed “the securities token platform”, Polymath is essentially the Ethereum of the traditional finance/securities world. With plenty of scope to facilitate worldwide securities transactions, this digital currency is worth taking a punt on.Cardano (ADA) is currently ranked as one of the top 10 coins by Coin Market Cap, with an individual coin valuation (at the time of going to press) of 30 cents. It’s a fully open-sourced, decentralised public blockchain project. The creators of Cardano claim the technology is evolving to be a smart contract platform which will deliver more advanced features than any other blockchain protocol. Like Ethereum, it offers the potential for other cryptocurrencies to be built on top of it – something which crypto speculators see as a positive feature in any new or relatively new project.A small market-cap coin, Simple Token (OST) is designed to help small businesses onto the blockchain . It’s a fantastic project with a white paper that ticks all the right boxes. With the company ready to launch their OST Kit Alpha set to launch this month, now is the perfect time to get involved with Simple Token.