KCNDreams The Store downloads from another computer may work, and you can certainly try them. But it's more likely they won't work, especially if you use the EA App, so it's probably best to download fresh copies. Sign into the Store site and click Store > My Store Account > Purchase History.
As for what to buy, what do you like? As mentioned, do you have some items from sets where you might want the rest of the set? And check out the spreadsheet in the second post of the master Daily Deal thread (sort by Oldest to make sure you're viewing the right post) to see whether any items or sets you'd like ever go on sale, and if so, when.
Daily Deal (DD) 2018 Rotation List and Sales Help | EA Forums - 1821670
You can also list some items or sets you'd like, here or there, and ask for help figuring out the cheapest way to acquire them.