Can a once truly saved believer backslide too much and lose the gift of salvation? If so do they need to repent and ask for forgiveness through Christ again? Thoughts are welcome and scripture too!
Probably. A person can be saved from any other danger and end up back in the same danger again.
If one imagines "saved/salvation" as being a permanent stamp place upon someone that grants them permanent immunity from loss, then by definition, you cannot lose your salvation, otherwise there would be no immunity.
However, does the Bible describe salvation/saved in terms of immunity from loss? it does not appear to do so IMO. So I would be reluctant to assume salvation/saved implies permanent immunity from loss. The Holy Spirit is given as a downpayment on the eventual redemption of the body "until the day of redemption.
So, that downpayment seems to have an expiry date, and not to be universally permanent. We have the Holy Spirit, and we have His assistance to prepare ourselves as a bride for the wedding day, but if we do not cooperate with the Holy Spirit in His efforts to prepare us for the first resurrection, He may just move out on the wedding day before the wedding, and we may find ourselves standing alone at the altar of our idol, while others are meeting the Bridegroom in the air.