well, just a brief explanation on why Loki.
Loki is a must for end game content.

Want to clear Alliance Battle? You'll need Floki
Want to have an easy World Boss kill? You'll need Floki
Want to stay undefeated at Battleworld? You'll need Floki *on manual play

Of course you'll only reap the rewards of using Floki at 6* , below that Floki isn't much of a use.

Just have a look at the Hero Ranking for Story Mode and World Boss.

edit:- don't use anything on Sif, she's just an extra fodder to use at Co-op to gain more materials.

Our legendary Davidtcf will be trying it soon. We shall wait for his verdict.
all uniform has it's use. if you're gonna main Loki, then the uniform will further boost your Loki.

Silk and Carnage are Alliance Battle and World Boss materials as well. Highly recommended once you're settled on a main character

But i'll suggest to use the Rank Up tickets on Loki and use the selectors to get Loki bios to push his gears past level 15

login even should give a 6* rank up ticket as well on day 7

update takes place at 2a.m, clear your energy before the update.

new players have a one off option to purchase uniform for 500 crystal if i'm not mistaken. after that they're the same like us

Good if your cards can grant you +20% skill cooldown to keep Silk's shield up continously