Im not sure how you guys play Abbadon as he is a very versatile hero to say the least. When I pick him i generally have a mindset to support and end up carrying a team when the carry fails. He has the ability to scale very well but be wary he can be easily countered and kited.
let start with the starting items and progression.
Starting items 2 x wards, courier and a little sustain for the lane.
I love going urn cause you for the pure stats are heal especially if you have a fighting carry like PA, stack her with Aphotic Shield and watch the charges rack up. Vlads and MeK give nice fighting and team sustain.
Situational items dependent on the position in the game and opposing heroes i do seem to side towards the Scepter and Book especially with lager team fight opposition. if im front lining later on then you’ll go heart for the carry to clean up.
The talent tree
This is very much based on situational and in what lane you are playing having said that there are a few of the talents I would not change, at level 6 I always take the damage helps with last hits if in off lane or taking a few neutrals alone the way 15% is way to low to be considered. +5 armour, 15% cooldown reduction and +200 shield health will ensure you maximise your support and keep your fellow team mates alive.
In conclusion don’t feel bad trying to play Abba as a carry he has the skill set to do really well however will fall off in late game when other supports are able to kite him and his abilities. He is best from lv 6- 16 I would say allowing his full skillset to be taken advantage of.
Goodluck a real worthwhile hero to get good with and your team will thank you in the long run please comment if you have any suggestions