One that fits in a jersey pocket for emergencies, or is CO2 cartridge better option?
What else do i need? mini tool, inner tube and food?

Don’t want to mount pump on bike if possible.

How far are you planning on going?

I dont take anything except my mobile and wallet if Im doing a two hour or less ride.

If I go for longer I may take a biscuit and a drink.

Similar to mountain bike for me.

In Saddle Bag; Inner Tube, Punture Repair, Speed Lever, Multitool, Speed Link, CO2, Money.

In Pockets; Food and Pump if i’m riding solo

I take topeak pocket rocket + co2 + tube + leavers + food

Topeak Mini Morph will sort your pump needs…..

I have a surplus one of these :

http://www.topeak.com/products/Pumps/MicroRocketAL if you are wanting a cheap one ! pretty scratched up from being in pocket and seatpack, but has only actaully been used 3 times

Lezyne road drive for me.

I hate stuff in my pockets, so commit the sin of a tiny Specialized seatpack:

Tube
Self adhesive Park patches
CO2 cannister + head
Tyre levels
Chaintool
Chainlink
Allen keys

just bought one of these

blackburn mammoth sl pump

CO2 mini-pump, Spesh seat bag, 2 tyre levers, mini tool, quick patches and tube.

All in kidney pockets:

Blackburn airstick
Tyre levers x2 (only deploy them if you can’t physically rip the tyre from the rim with your bare hands)
Inner tubes x2
Sweat rag (in hot weather…useful for cleaning lenses too)
mobile phone & wallet (both in sealed sandwich bag)
multi-tool

I have in the past used a small saddle pack for most of the above, which left kidney pockets free for home-made flapjack. Useful on the 4 hour + rides I used to be able to do…

For winter 2 X Co2/tubes/levers + mini pump that realistically gets you up to about 35PSI.
For summer 1 X Co2 & tube.

Oh and mobile wrapped in a Buff.

Lezyne road drive for something that will fit in your pocket, maybe CO2 as well if you don’t want to hang around long (I use a Topeak road morph on the frame during winter for that reason).