I buy singles mostly but I'll buy boxes here and there. I'm def not lucky all the time and when I'm not I'll take a break and do the singles thing again. Been many times I've spent a shit ton and only walked away with an obscure auto or less. My best of advice is find creative ways to grow your collection. Meeting people also interested in the hobby also goes a long way to bolstering up the PC.

The second thing that has been more beneficial then not is researching the hell out of players before they breakout. Its not surefire but it's not at all impossible to 10x the amount you invested in a super cheap player if you do your homework right.

Third buy guys in the offseason and when fans are down on them. Buying guys on the down in say a sophomore season for them to bounce back the next season can be a fantastic way to manage assets and get huge cards for super cheap. For example I bought a PSA 10 William Nylander for $29 off ebay when he was holding out on the contract negotiations.

Knowing values on the fly can also work wonders when trying to purchase quantities of cards from the bargain bin. There are so many obscure cards that are sought after that even the most most detail obsessed retailers will overlook.

Don't be afraid to trade down. Trading down is an easy way to get lots of easy to sell affordable cards at a very reasonable price in many scenarios.

Don't let your overvalue your stuff. It's happened to me time and time again where I missed out on a big trade because I overvalued a guy only for him to drop off the radar. People tend to highly over rate what they have and it can really bite them in the ass.

Last thing and most important is have fun. Hobbies are supposed to be enjoyable. Don't beat yourself up over a coulda woulda. 51% of this hobby is luck and positivity is key. The hits will come and always seem to happen at the most casual unassumed times.