Ranger dip or Alert Feat? I'm playing a champion fighter and am currently level 7 approaching level 8.

I want to get the Alert feat but I also want to dip a level into ranger for favoured enemy and a little bit of natural explorer while we're at it.

I'm obviously going to have to pick one and hold of on the other one for a level.but I'm not sure which one.

any advice?

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for context on favoured enemy:  
My character is a high elf hunting a drow assassin