The single advice I'd have for you considering this type of collar is that you ought to realize, to your core, and accept, in full, that as a Gorean kajira, you will be actually viewed as a chattel slave. NOT as a "slave in the BDSM context of thing, who agreed to pretend some of their rights don't exist for the duration of the relationship" but as a class of human being whom morally has no claim to rights, regardless of whether society grants them or not".
You will be viewed as genuinely different than your owner, in a way that Westerners would perceive as being 'less then' (though Goreans wouldn't tend to describe it in those terms, instead merely acknowledging it as 'different than').
Think class differences in Victorian Britain, between the ruling class, and the poor, and how the aristocracy genuinely believed they were naturally distinct and superior to their servants.
Think colonial slavery, and how the white plantation owners genuinely believed they were genetically preordained to own and rule anybody with a darker skin than their own.
Goreans think that way about the distinction between those who are naturally inclined to be free, and those who are naturally inclined to be slaves. Declaring yourself a slave in the presents of a Gorean Free (or being owned by one) will make then actually put you in a different class of human being as themselves.
You will not be seen as "an-equal-human-being-who-has-merely-chosen-to-submit" as most of the BDSM community sees slavery.
Presuming a Western upbringing, this will be something you're completely unprepared and unfamiliar with. It will evoke very strong emotions, most of them very negative, unless/until you can accept that, unlike in Western thinking, this class distinction doesn't express a negative value judgement in and off itself. (Instead of Western mentalities, the Gorean value judgements lay in how well you express all facets of yourself in line with the class you naturally belong to, which is backwards from how you're probably used to thinking about such things.)
If the path of acknowledging yourself to be a different class of human than your owner is one you're unwilling to take, and your kneejerk reaction to that idea is one of anger, instead of fearful recognition, I'd advice you to stay away from anything that even remotely looks like a Gorean collar.
If it is something you're willing to embark on, then the only thing you should know before entering a collar is that -considering the fact that you are entering into a relationship with a person who morally sees you as 'rightless' instead of as somebody merely 'giving up rights'- you will be completely at his mercy and his whim.
There is no point to trying to guess, speculate, or anticipate, what your life with him will look like, because he may change what he wants from you at any time.
Focus merely on being exquisitely beautiful and absolutely obedient in everything you do instead.
I can be your whore
I am the dirt you created
I am your sinner
And your whore
But let me tell you something baby
You love me for everything you hate me for