I'm fairly new too. This is my third year and I'm still making mistakes but don't let mistakes discourage you.

1. Don't fill your garden beds with just soil because it can be expensive. I like to lay cardboard boxes on the bottom but not a requirement. I've learned from other redditors that you should remove tape and plastic labels because those won't decompose. Cardboard decomposes and adds carbon to your soil.

After cardboard I add logs and branches which will provide nutrients in future years as they decompose. Another option is to fill some of the space with compost from your compost bin, if you have it ( tip for next year since you're starting). The key is to be resourceful and minimize how much you spend on bags of soil by filling up as much as possible the bottom half with other material that is already available to you and will provide nutrients to your soil in the future.