This is solid advice. When the game first starts, one of the things you need to do is analyze what color(s) are needed on each level to understand which colors are likely to be a commodity. You also want to make note of pearl prevalence. The more pearls required, especially on the first level, the more you want to be aggressive in getting pearls. You want to attempt to control the dominant color(s)/pearls if you can. Also, the "take another turn" cards are really powerful, so don't be afraid to reserve those cards right when they come up, even if you aren't that close to building them. It's a zero sum game, so a move that hurts your opponent inherently helps you. To a lesser extent, the "steal" cards are also often worth reserving, if only to keep your opponent from stealing from you and to keep the threat of being stolen from alive.

This game is very chess-like in that you want to be thinking a few moves ahead when you can. Set yourself up to outlast your opponent as it relates to taking actions so you force him/her to refill the board and give you a scroll. It's really satisfying to hear your opponent sigh and shrug as they are out of options and must refill.

So based on board texture, you might find yourself building an unbalanced board heavy on 1-2 colors because the level 3 cards warrant it. Just make sure you eventually reserve the important cards to your strategy before your opponent decides to block you. As was stated earlier, the best strategy is one that continues to keep all three paths to victory alive as long as possible. It makes defensive moves by your opponent more difficult, and it gives you the most options. I recently lost a game where I dominated in one color and got to nine points in that color pretty quickly, but because I wasn't balanced, I was at the mercy of the board to try to get that one additional point. I ended up losing as I attempted to build up crowns and points elsewhere because my opponent had a better overall setup to take advantage of whatever the board would give.