Hey there. First just want to give some housekeeping tip on your mason app. Using hidden tags around your images can keep your app nice and neat. Makes it easier for you to just edit your first post and add more build images to the first post and keeps it easy for everyone to view. And adding tags Like "First Build:" before it is nice too. Heres an example ;D
First Build:
Image in here, hidden by the hidden tags
Second Build:
Image in here, hidden by the hidden tags
Also don't be afraid to use more then just gravel blocks while building. When building structures try to pick out a primary block, which you will use most often, like for the walls. Then pick out two accent blocks that you think complement the primary block well but don't clash with each other two much. You can use your accent blocks as borders for walls, windows roofs, whatever you set your mind to. Also adding depth and shadows to builds will really make your build pop! Also building bigger more detailed things is a defining aspect of many masons. And as you start to build bigger you may be using many, many different blocks, your primary and tertiary.
Some other advice would be to add some curves, straight 90 degree angles are okay once and a while but we like to see that you can get away from that and build some cool stuff. Some additional tips would be think of some non-generic things you could build. stuff that others aren't building. This will really make you stand out. For example houses, apartments, castles, things like these are seen quite often so they have to be very outstanding or out of the ordinary to impress the big boys and girls upstairs ;3. To get some ideas of what masons build feel free to look around some of the mason worlds as well as the masons personal worlds.
These can help out greatly when aiming for mason. Keep playing and building and soon you will be on your way to mason.