Do you have a hireling? If not, follow this link to get a hireling without spending money if you can do the surveys. Many thanks to @moxyll for this information. The link I provided from @Skaul would really benefit you greatly.
In the link I provided, I also recently helped someone with a Rogue build. Scroll up to the top of the discussion and read all of the information and follow the links embedded in the discussion for more information. The falling items you mentioned are either meteors or someone using a bombard mythic. In the link I provided, there is a list of mythic items, which gear they can go on and the myth stones you need to make them. There should be a lot of information in the link above to help get you started. There is a lot of depth to this game and it takes some time experimenting with gear, staying on the forums and figuring out what you like to use.
Bottom line, there are 42 affixes available for each character (6 for Mainhand (MH), Offhand (OH), Chest, Cap, Ring, Amulet and pet). There are also 4 talents for your chest, Cap, Ring and amulet (you can change talents with Crystal stone citrine). In addition your gears, except pet, has natures that can be changed to give you a boost using Crystal stone Beryl.
Take out a few minutes to look at what @Griffin012 has put together on crystals.
More information from @Griffin012 on mythsones.
Here is a link to natures.
Link to mythics.
My suggestion is that you focus on farming and experiment with various legendary gear as it drops. Feel free to ask questions as you progress.