Instant-access exchanges offer speed and anonymity. You will most often trade your cryptocurrency against another at a fixed rate, but without the hassle of having to set up an account on a full exchange, without having to fund balances (you must use your own wallets – more on wallets below), place buy/sell orders, then withdraw to your wallet. You will have to provide two addresses (in cryptocurrencies, addresses are where your funds reside to make it short): a payment address (for the cryptocurrency you want to purchase, i.e. the address of your target wallet) and a refund address (the address from where you are sending the money from, in case the exchange order cannot be fulfilled. These exchanges are for example Evercoin, Nexchange, ShapeShift or Changelly (Changelly is not anonymous though). Some of those will even allow to purchase cryptocurrency with fiat currency.
Dollar-cost average: This sounds complicated, but it’s not. Dollar-cost averaging means investing a set amount of money at regular intervals, such as once per week or month. That set amount buys more shares when the stock price goes down and fewer shares when it rises, but overall, it evens out the average price you pay. Some online brokerage firms let investors set up an automated investing schedule.