Need mentorship/Advice

Hey, I just got FT offer from the place that I did a summer internship at. Its a mid-tier consulting firm and I am getting into a Turnaround&Restructuring department. I loved the job and all, and I am happy that I got the offer.

But, I also had this feeling that I kind of fell out of the competition, as I did not get into MBB or BB. Tbh, it was coming from the paycheck. When I got the offer, I had no idea whether it was good or not. But, the moment I realized that the pay was lower than those of MBB or BB. (its 70k a year), I felt a little disappointed. I know its due to my lack of effort and networking.

But, I really wish to know what I could do from here If I want to climb up the ladder. 

Ultimately, I want to get into PE company in the long run and I want to do anything I could do at this point in my life to get prepared.

All the BB interviews are closed and honestly, I do not have the gut to decline the offer and look for better ones. 

Please advise me if anyone went through this path, because it might sound dumb and trivial, but I feel like my confidence/ambition is falling apart. 

I heard that lateral hires are quite difficult after graduation. I am just wondering whether it is possible for me to work at less prestigious firms for a few years and laterally move to different firms for the same position.

Honestly I feel like I am behind my competitors. Please let me know if you guys have any advice. I greatly appreciate it.