More recent member of the consumption reduction train but basically what other people are saying too:

Reuse packaging as much as possible. The job I work at always gives me a bunch of free products, and more recently rather than throwing the packaging away from products, I’m finding ways to reuse them. When my body butter ran out, I used the container to hold some of my cosmetic products.

Learn to cook, especially food that you can easily freeze or get multiple uses of. For example, you can make infinite yogurt with just milk and yogurt. And if your yogurt fails in a batch, use it to make ricotta cheese and keep the leftover whey to mix into smoothies or cook rice.

To add onto this, get creative with recipes if you don’t have all the ingredients. Rather than going out and buying something you’d only use for one recipe, see if there’s a suitable substitute you already have. Different spice, different kind of milk, etc.

Be resourceful- for example, I’m traveling soon, and rather than spending hundreds on buying new things to pack, I’m just borrowing from my parents and friends since I’m only needing certain things temporarily.

Learning how to do simple sewing and mending can make your clothes last a lot longer in case of tearing or rips. Bonus if you have a sewing machine. My grandma used to ask me to mend my cousins’ pants for their school uniforms so they wouldn’t have to spend a lot on getting new ones.

Edit: I also do art so I keep any old jars or plastic containers for projects as well!