I collect what I like and what I could afford. I enjoy researching the coin's history and then finding the coin that I want as much as having it. Once you pick what you desire then you should make the decision do I want to buy as many as I can afford or would I be more happy with saving my fun cash to buy the best of that coin and have fewer but more desirable coins. Take your time and once you decide if you want Mogans, buffalo nickels, etc.. Post your questions on that coin topic and I am sure you will get many leads on what to do next.
Read...read...read....you need to buy some books and learn how to grade...buy books on the coins you think you want to collect. Ask any questions on this forum you may have.... A few rules about coin collecting.... Never clean a coin... (unless it has PVC ) Hold the coins by the edge (or rim) other wise with a Un-circulated coin you will get fingerprints on it and lower the value. The best advise I can give is to read and learn. Speedy
Look for, find by searching/or buying any coin YOU like and can afford. Buy with the intentions of keeping it forever. While this may not happen, at least start out this way. Buy the grade of coin you can afford, and not just any coin which you may intend to trade/sell and upgrade. Upgrading will only cost you a lot of money, so do it right the first time. You might start with the "keys". Try and find anyone near to you to share in the joys of coin collection. Its a lot more fun if you have company Put as much or as little time as you can manage, and make sure that each second in enjoyed. Do it right and GOOD LUCK!
See if there is a coin club that meets in your area, most towns have one. Learn what you can buy studying and don't be afraid to ask questions, there are no dumb questions.
This, IMO, is the most important thing of all. Not just because that's the whole point of a hobby but because spending the time to enjoy your coins, ie, learning about them is a constraint on efficiency. The internet is wonderful and it makes the collecting possibilities almost unlimited. The problem now I think is that it's too easy and too fast. Even the hardest items to locate are still easier and faster to locate now than before the internet. It's all very efficient now and that, IMO, is a problem that will only get worse. For all the marveling we do about efficiency, IMO, it's just the fast lane to entropy. In other words "burn-out." Buying efficiency is constrained by the time you spend studying and researching what you have bought. You won't burn out and you'll enjoy your coin collection, as your suppose to.
While cost is important, it's also important to go with something you really like and that interests you. You can collect circulated or unc or even have mixed collections. There are world coins and ancient coins. Don't get in a hurry. If you must start right away just put to- gether a set of something really cheap while you're getting your feet wet. Read and try to learn a little about the market. Get a feel for resale value by looking at the buy ads of the coin companies. Sell a coin once in a while to really learn about the market.