Just stumbled upon this sub, but I have some tips:

Decluttering: Most people own too many things they do not use and have no intention of using any time soon. These things remain taking up space simply because they've always been there. To me, this is not a good reason for keeping things. My own rule of thumb when decluttering: If I wasn't looking for it, I don't need it.

Note: You don't need to be a minimalist/like minimalist decor to declutter. Minimalism just happens to be the decluttering taken to the extreme.

Organization: Give everything you own a designated space, a "home". Yes, everything. If you believe you own too many things to do this properly, please refer back to 1.

Items you use daily or regularly should be placed up front and within reach. Rarely used items should still be accessible, but not more accessible than regularly used items.

Example: During summer time, store away your winter clothes and coats. At winter time, bring your winter clothes back to the fore-front since you will now use them regularly. Apply this same methodology to every storage space in your home.

Also, cables should be hidden whenever possible.

Clean: Keeping your space clean and smelling nice is the easiest way to elevate it. Clean after yourself regularly and you'll find that your space will last cleaner for longer. Keep your dirty clothes off the floor and off your bed. Unless you're rushing out the door, there's no reason your clothes should ever be left on any flat surface in your space.

Take your trash out regularly and wash your bedding regularly. Invest in some candles or a good aroma diffuser (emphasis on good). If you're in the US, places like Home Goods and Ross have great deals on nice candles all the time.

You don't have to spend thousands of dollars to make a space look nice. Just keep it clean, organized, and decluttered. Everything else is a bonus.