Don't bother with a travel system.
A baby in a car seat is insanely heavy - honestly I struggled to carry ds to the car! They are only laid flat for such a short time, don't get a big bulky system because it'll drive you insane.
Look for something light, stable, reversible (if you want) that folds easily, preferably one handed, and folds compactly. Decent hood, decent basket. Lie flat seat (not bucket type.) most have snap on bassinets or pods you can put them in while tiny, but ds was in the seat from four months - afyer that you need something easy!
Easywalker mosey, babyzen yoyo, m and p armadillo flip xt, babyjogger city mini. Uppababy vista, nuna mixx ... that's the sort of thing to go for. Exactly what you get will depend on your lifestyle - central London is going to be fine with a small buggy whereas if you live in the country try you might want something more robust for walks.
But avoid travel systems.