One of the basic strategies that you can look into is buying at the right time. It is natural to buy cheap when there’s a surplus of assets lying around. The challenge is to know when the supply is greatly ahead of the demand. Profit can be easily made with the gap between the cheap purchase an expensive sell. Another ideal way to purchase coins is at the time when ICOs (Initial Coin Offering) is introduced.
A “manageable amount” is obviously subjective and will vary for each person based on things such as time available to dedicate to trading. Feel free to do your own research to find the right exchange for you. I tend to value user experience of an exchange over the amount of coins on it. Ultimately, what exchanges you use is going to depend on your own personal preferences. GDAX and Poloniex will provide sufficient resources needed to be a successful trader, so they are definitely a good place to start.
Mean reversion is where the investor assumes that the price of a coin will remain at an average price level over time.  Upward trends, and downwards trends, are expected to revert back to the average over the long haul. This means you need to know the charts well and be able to figure out what the average price for the cryptocurrency you intend to trade in. When the coins are less than the estimated average that is when one wants to make a few purchases. When the price is higher than the average it is expected to drop back down to the mean price and that would be the time to sell.  Of course, figuring out just when to sell is the trick, and that is where the gamble comes in.
It is important investors realize not all exchanges and brokers that offer delivery of the underlying Bitcoin are created equal. Some firms have fallen victim to theft by hackers who have stolen Bitcoin belonging to clients whose money was held at the exchanges. Meanwhile, other Bitcoin exchanges have gone bankrupt (as in the case of Mt. Gox),  as a result of fraud or mismanagement.
No, the successful trader is not me. I’ve gotten lucky a few times and I’m still refining and trying out strategies; on the other hand, I’m part of communities of people who trade on a daily basis to grow their portfolios, and while some of the results can be attributed to luck, a majority of it is based on fundamentals, good habits, and experience.