My friend Joan makes great points! Don't DIY if you don't know what you are doing. To add to that, don't DIY anything requiring licensed trades ie electrical, plumbing, or HVAC. In Texas our contracts say for the repairs a buyer requests that they must be performed by a licensed professional. But even the faintest of bad decisions ie too much gray can throw your home off the list. Be smart. Get a second opinion before making these decisions.
When you have quite a few buyers, you end up viewing many homes, and all kinds of updates and remodeling projects. Do all of them increase the value of their home?
OH MY NO! Just because you like slate, it SHOULD NOT be all over the home - floor, countertops, backsplash. It was too much. You really like accent walls, so you did one in each room of the house -- all different colors. Buyers are most likely thinking - we need to buy lots of paint to cover up all those colors! You see hardwood flooring in a home, then when viewing you see some is sand & finish wood, some is engineered wood, and some is laminate. This sure stops the flow, and doesn't look good, let alone the height between these types of floors causing trip hazards.
You wanted to try tiling a floor, and you think it turned out very well. BUT, there were definite uneven gaps between the tiles and nothing on the edges.
There are some homes you have to shake your head when you see the DIY projects, and know they should have called a professional to do these updates/upgrades. Even painting can be a disaster with dark paint on a white ceiling all over the room! Not everyone is a great painter!
Bottom line - if you KNOW how to do some things, great.....it probably will be fine. If you are learning, maybe do the tiling on a board in the garage first, then the bathroom or kitchen floor. If you have thought about selling after these DIY projects, you may not have as many buyers interested in your home, or you won't reap as much as you could have if a professional had done the job.