The most senior trips are the higher time three-day trips; most junior are the low time trips (LGW,MAN,DUB,SNN). The four to seven day trips tend to be spread out through the mid to lower seniority range.

Moscow is a seven day trip in winter- it goes pretty junior. I expect that the long Africa trips will go junior. The S.A. flying goes junior, but may not be a long enough trip for you.

I doubt that you'll need to buy tickets to get to work between the LGA and JFK flights.