I've no experience in mining whatsoever, but I've been day trading cryptos among other securities for years. There's no sure way to win of course, but a few tips to keep in mind
-diversify, big cap alt-coins tend to swing against BTC, so if BTC is losing you can bet one of the others will gain. That's a good way to hedge
-steady hands, cryptocurrencies are volatile like no other securities except maybe leveraged VIX trading - don't freak out and panic sell if you're down for a day. The market is a mechanism of transferring money from the impatient to the patient, sayeth Buffett.
-don't try to day trade if you don't know what you're doing/are new. You'll save money on transactions and generate more return by just holding a well diversified portfolio.
-occasionally transfer gains back into fiat and to your checkings. It'll give you a sense of security and make it more 'real'.
Lastly, you can start trading with any amount but of course the more you've got set aside for it, the bigger your potential gains. But don't put in more than you can afford to lose reasonably, like I said it's very volatile.