While aspen is a favorite amongst most, you can also experiment with different substrate over time to see what fits better in your budget and what you/your BP prefers more (even though BPs don't necessarily have a preference, its more of a preference of what you like and what is more appealing). Not to stray you away from aspen (because I don't have anything against it and was a long time user of aspen), but experiment with using others such as paper towels/towels if you're on a budget. The only reason I switched to this from aspen is because of my budget and I found it's easier to spot clean messes, the aspen doesn't get caught in its mouth while feeding, etc.