I would definitely reccomend getting a second cat.
We only ever intended on getting one, but made the decision to keep Bella as a house cat and since we are both at work during the day thought it was only fair to find her a playmate. So we ended up adopting Ayala.
Bella was only about 6 months when we got Ayala, and I was told that a cat under a year old should take quite well to a new arrival, so I'm sure things will be fine for you. The introduction still didnt go smoothly though, we had to keep Ayala in a separate room for the first couple of weeks while she settled in, as Bella was quite angry about it at first. However now they get on so well, they play and sleep together. So it was definitely the best decision I ever made.
I would definitely try to ensure you have a spare room available for your new kitten though, even if its a small room where you can put food, a bed and a separate litter tray. Doing this will make the introduction process and first few weeks much easier, and will mean you can control their meetings and ensure the little one feels safe and not afraid.
We decided to get another girl as I didnt want either of them getting too big, and I felt 2 girls might get on better and be easier to introduce, although I'm not sure how true this is.
Hope this helped and good luck finding your new baby