No need. Unlike granblue you dont need a huge pool of characters to clear all content.
I understand this mindset but when you can clear all content easily with mostly 3* and few 4* stars its a bit meaningless. 1% makes 5* special and rare materials to evolve it later also adds a special feel. I'm playing JP ver for almost a year and rolled a lot of 4* and 5*. I'm f2p. I only bought premium currency once to roll on guaranteed 5* gatcha on New Year.
High rates make the game worse. Why? Just because the rate is high developers will make sure that you will
need to roll more often otherwise devs wont make money. I dont want to be forced to roll for 5*.
Here is the great list of servants guides:
https://www.reddit.com/r/grandorder/comments/5hc8p5/guide_to_mmm_links_ordered_by_servant_includes/
Also I dont think rolling 5* is a good idea at all. But you can do whatever you want.
Its not good because materials are too hard to get. And for example Jeannu is very weak until you max level her. Her real growth starts after level 60. Its not that easy to farm EXP in the first weeks. Also consider party cost. Any 5* will eat all cost and you will have hard time using other servants in the same party. I think rolling 5* at start is a mistake unless its a Waver
I will try to get 5* CE or just few 4*. Or maybe I will get initial roll 4* and play with it until better gatcha.