The big two that I promote:
Triage - It's right in my signature line. Yeah, I got tired of repeating myself about it, so it's in there for anyone who reads it.
Put simply, is it worth spending 5 hours coding "Blackjack" into your game, or can that 5 hours be better spent buffing the rest of your game in some other way? You can never get "time" back. It isn't infinite. It's a finite resource. You need to cut things that aren't working, not waste time on things that aren't worth the time you spent on it (by all means, if you can code Blackjack in 20 minutes and implement, good on you! But, you probably shouldn't spend 10+ hours on it if it isn't central to your game in some way).
Triage is important. If you can't make it work, you remove it. Or, you figure out how to fix it. If it's taking too long to fix it, maybe you "shelve it for next time".
Asset Purchases - It was already slightly touched on here. My advice on this is always the same: Use placeholders on all your assets until you have a completed game. Then, you do the "polish" phase, which is when you buy the assets you for sure, 100%, need for your project. There is little sense in wasting money on projects you won't finish or will continue to not finish after you have 8 or 10 of them started.
Save up some money during your normal dev cycle and when your game is "done", then you spend that cash requesting resources from artists. You will know exactly what you do and don't need by the end of your dev cycle, and you will have a very sizable chunk of cash to throw at a single artist so that your assets won't "clash aesthetically".
I personally recommend putting aside $5 a week from the start of your project until the end of it ($260 a year as a budget for assets for you!), but you can do more/less if you want. 10 years into my project and you can imagine how much I've got set aside for "assets", 'eh?
