Storage is not why you take log backups. You take log backups when the database is in full recovery model, and you need point-in-time recovery between full or incremental backups.
If your business can afford only 1 hour of lost data, then I'd typically setup nightly full backups for smaller databases, with log backups every 30 minutes during business hours (or even 24-hours per day).
If you had the database in simple recovery model, and each database was only a couple of hundred megabytes, you could simple take full backups every hour, or half hour.
Essentially, the decision comes down to answering these questions:
- What is my recovery point objective?
- What is my recovery time objective?
See Wikipedia for great details about what those two things actually mean.
If you're storing high-value, business-critical data in those databases, you should understand log backups, and the transaction log and recovery in general (link to my blog), to avoid being in a situation where you're unexpectedly missing data, or down for an extended period of time.
In your case, I would also do a log backup after every diff backup just to ensure the log doesn't grow out of control.