Seniority means a lot. Long story short don't dick around, make a plan and get there ASAP. Don't blow money but don't step over $50k to save $3,000. This might mean buying a bit of twin time, or getting your MEI ASAP, or going to a school that will hire you as a multi instructor at low pay to get hours (ie ATPs).
Also if your goal is to work 121 don't dick around doing anything else unless you want to do it. There are guys I fly with that have a great background but they are junior on a list taking the crap schedules. All the experience in the world doesn't get you 17 days off vs. 12. As someone who got to bid 1 & 2 for a long time, take it from me, you don't want to be junior.
Don't look at first year pay. Yes it sucks. No you won't feel valued (at least I did not). However once you get that over and done with, and have the ability to somewhat pick a schedule, it's a great job if all you want to do is show up, do your job, and go home IMO. It will be sad when my company, and the entire industry, shrinks considerably due to high operating costs. We have seen the job glory days already. Nowhere to go but down in this country.