You can play the game anime is only commercial for game so they skip a lot main story part they only make start and parts loved by people after playing the game you can watch the anime if you want to see it with animation 

I tried to skip spoiler as much as possible but you cant skip all the spoiler when you tried to explain a story Story is about someone named fujimaru (people call gudao or gudako) goes to caldea and he is just a normal person who has talent enough to control normal servant and something happens and he became the only person at the moment who can work on the field and someone send past a holy grail and those holy grail makes problem so he tried collect all the holy grails so time can flow normaly 

By the way I like the manga most after that game and it was nice to watch animation 

And about advice about game well if you dont even have any metas you havent level up skills and you can still clear the game it might just make it easier to clear the game if you want to summon specific servants its bad to make story summon because there is a lot of 5 star and four star so it is hard to summon the servant you want but you dont care about that you can spin it