So, I've never played a FIFA game...
I picked career over this FUT thing.
What's FUT about? I always thought it was like a career mode? But perhaps not...
It's a cross between a career and collecting sports cards/stickers. You earn coins through playing games, and can use those coins to buy packs which contain random players. There are consumables too, like each player has a number of games they are contracted for, and you can top up with contract cards.
I've only just started playing it for the first time so I'm a complete noob myself, but it's very addictive. Some good early advice I've been given is to not actually spend your coins on packs. It's a thrill opening one up and hoping to get that amazing player, but it's more cost effective to go into the transfer market and buy players you want with the coins. There are daily and weekly objectives which can be things like 'score a goal with a player from France' or 'score from a cross', and they can give out coins or packs as rewards.
The Squad Battles are something new this year but I'm making a lot of use out of them. You can play against 4 random squads a day (this number increases to 12 on weekends), and you get coins for completing games, but you also get squad battle points for them. At the end of the week, you will be ranked against everyone else and can get some good coins and cool packs as rewards depending on what bracket you came in (top 1%, top 9% etc).
Also, if you're going to play, use the companion app/web app. You can use it to check the daily objectives, to look through your squad, and eventually you unlock the ability to use the transfer market through it. Right now there are daily rewards such as packs or coins for logging in to it each day.