When buying coins, and especially with Bitcoin, you will notice that your purchase is in decimal. A Bitcoin itself is relatively expensive, around $10,000 at the moment (as of 15th Feb '18). If you were to purchase say $5,000 of Bitcoin, you would at today's rate be purchasing around 0.5 of Bitcoin. Do not ever worry about this; Bitcoin operates at eight decimals places. You do not need to own a whole Bitcoin or any coin for that matter. Consider it like pence in the pound or cents in the dollar, but with more decimal places.

Co-founded by Tyler and Cameron Winklevoss, Gemini is a fully regulated licensed US Bitcoin and Ether exchange. That means Gemini’s capital requirements and regulatory standards are similar to a bank. Also, all US dollar deposits are held at a FDIC-insured bank and the majority of digital currency is held in cold storage. Gemini trades in three currencies, US dollars, bitcoin, and ether, so the platform does not serve traders of the plethora of other cryptocurrencies. The exchange operates via a maker-taker fee schedule with discounts available for high volume traders. All deposits and withdrawals are free of charge. The platform is only fully available to customers in 42 US states, Canada, Hong Kong, Japan, Singapore, South Korea and the UK.
In order to keep your crypto investments safe, you can keep your records in a separate hardware wallet and keep a track of your trading stack. Features of some cryptocurrency exchange platforms may vary from other platforms and that’s why it is important for you to find the one that matches your needs. Once you are sure about the exchange that fulfils your requirements, go ahead and trade.
Don’t be greedy. No one ever lost money taking a profit. As a coin begins to grow, the greed inside us grows along with it. If a coin increases by 30%, why not consider taking profit? Even if goals are set to 40% or 50%, you should at least pull out some of the profit on the way up in case a coin doesn’t reach the goal. If you wait too long or try to get out at a higher point, you risk losing profit you already earned or even turning that profit into a loss. Get into the habit of taking profits and scouting for re-entry if you want to continue reaping potential profits.