Every time you need or want to buy something, write it down on a To Buy List. Go through your calendar for the next few months and add any gifts you plan to give.
This list works two ways. First, make a promise to yourself to buy only what's on the list. Use it to organize and consolidate your errands.
The second item is what you should do periodically. Go through your To Buy list and think really hard whether you really need the item. Think up ways to make it yourself or use something you already have. See how many items you can cross off your To Buy List before you spend money on them.
Since you have planned ahead regarding gifts, you may have time to make a gift instead of buying something more expensive. Or you might learn of just the right gift for someone by finding out what they'd really like or need. You will also have had time to mull over the things on your List because you'll see them in writing every day and have time to sleep on it. Also you might see a sale on an item you know is on your List. Having it in writing helps you remember and stay the course.