If you know for sure that a Maxi Cosi car seat will fit onto the Venicci pram then you can also use any infant car seat from Joie (except Juva), Cybex, Recaro (Except Zero1 Elite), Besafe, Nuna or the newer i-size Cosatto model, because these car seats all use the same adapters.
The Cabriofix is a good seat but it's an older design now and newer models on the market offer more in terms of side impact protection etc.
Most stage 2 seats don't need a separate base. Buying a base at this stage to last until the second stage seat is a bit of a marketing con because they are hoping to make you feel trapped into that second seat purchase. Plus as tea says, you might find that your baby is big and you want a larger stage 2 seat. additionally, if you plan to have another baby within abour four years it makes sense to have the base for the baby seat not be in use on the toddler seat, as you may want it again for the baby one in use by baby 2.
I actually find the base is often more expensive than the car seat - so it might be worth looking at the combined cost of both rather than looking at the car seat first (which was maybe the mistake I made).
Best value/cheapest would be the Joie Gemm + Clickfit base, or i-base if you prefer isofix to seatbelt fitting. The Gemm is also a large seat which may last a long time, if you want to get the most out of this stage. Con: Quite basic.
Best infant car seat for safety in the last few years' testing is Cybex Aton 5 with Cybex Base 2, or cybex base 2-fix if you prefer isofix to seatbelt fitting. Con: Fairly small seat and headrest not great for newborns (But straps often fit small newborns well).
Maxi Cosi (Pebble Plus, Rock or Cabriofix) seats are often on offer and I think the doughnut-shaped headrest on the Pebble Plus is actually the best shape for newborns. Con: Expensive, not the longest lasting seat, as it's i-size. (Cabriofix: Older specification seat, less safe/comfortable than modern seats)
Joie i-Level comes with its base included (making it cheaper than many other seats) and allows the baby to lie much flatter in the car which is better for their breathing. Con: Can't fit it with a seatbelt, which most other car seats can as a back up.
Cosatto Dock worth mentioning just for the lovely fabrics and patterns, if you like that sort of thing, plus Dock base. Con: Expensive, and not the best reputation for safety.
If you're not getting the pram and car seat together on a super duper offer, it might be an idea to buy separately, research stage 2 car seats first, as this might give you a better sense (conversely) of what you want out of stage 1. BUT you can overthink this a bit. It's hard to go wrong with a stage 1 seat. They are all pretty good especially if you stick to well known brands.