As a person who has been making games on Roblox for a few years now, and recently having started to teach my friend how to do the same, I have made a list of beginner mistakes I made when I first started using studio. Fell free to suggest more!
1# Forgetting to anchor parts
Every physical object in studio has a property called anchored, it is a Boolean value (true or false) that determines whether a part will be affected by gravity or not. If you set it to true it will stay in place and not be able to be pushed or fall. If you set it to false it will fall it if there is nothing under it, and can be pushed around when players walk into the part.
2# Turing snap to grid to high or off
To easily line items up, or move them a precise distance, use snap to grid.
The snap to grid setting is located at the top of the screen in the Model tab after the tools.
You can change the snap to grid setting for scale or rotation depending on what you are trying to move.
Note: sometimes, if you turn it up high and forget about it, when you drag parts they will go really far away or into a wall at the other side of the map, so make sure to remember if you have it turned on (or keep an eye on the snap to grid options)
#3 Closing important windows
Under the view tab, there are a list of different windows that you can open such as explorer, properties and output, that are important to keep open when making a game.
Look at the roblox docs page of the view tab to see which tabs you should keep open.
4# Not publishing updates
In order to update your game, you need to do more than just hitting the save button.
If you want to be able to play your new updated version of the game, go to the top right hand corner of the studio window and click on file, then hit publish to roblox or publish to roblox as to publish your updated changes to your game.
5# Not setting products on sale
In order for players to buy products in your game such as gamepasses, developer products or subscriptions, you need to set them on sale. It is easy to do this as all you need to do is go to your developer dashboard, select the game you created the product in, go to the associated items tab and choose the item you want to put on sale, then head over to the sale tab, put it on sale, and choose a price.
If you use the ID of the gamepass, and it is not on sale, you will get the error message: “this item is not currently for sale, your account has not been charged” when attempting to buy the item in-game.