Well if you are working in a startup, it feel like things start to get out of control, there are a bunch of decent free choices. I've used Trello for years and it is a good way to have Kanban cards and is a nice overview of the projects. Also it is free and sharing is super easy. The main tips are:

1. You should use the organizations to organize things and keep it simple, just have a monthly scrum chart that has the simplest possible organization with a backlog, what's in progress, what's blocked and what's done and dropped.
2. Here are the big tricks. Don't put anything into in progress that you aren't working on right away. You basically don't want to flood your mind with in progress stuff. And you do want to sort it so the most important thing goes first.
3. Use the members feature to assign items to people and the due date so you know when you have an issue. A huge list without any priorities or due dates is pretty much a mess.
4. The thing doesn't scale in terms of views, so it is most useful for the big overview.
5. I personally like to grade how much time things take to do. This is not a full scrum, but good for personal management. My personal metric is in half hour chunks, that is 1 point means it would take me about 30 minutes to do. And instead of big estimates, I stole something from somewhere which is to use the fibonacci series to schedule times so that means a ? if you don't know, then it goes 0.5, 1, 2, 3, 5, 8 etc to figure out how many hours something will take.
6. Scrum for Trello is an awesome extension. There is a Mac App for Trello (which is really just Electron underneath I think), but it shows the so called burndown and let's you manage it. Tells you how much time you've used and what you estimated. The simple convention is to put the (estimated) in parenthesis and the [actuals] in brackets. The chrome extension works great, but Safari doesn't seem to work
7. Do your Chrome because of the above problem. But once you invest in it, you can see the number of hours that you have booked into in progress and that should help you be more efficient.

Asana is a little different, it doesn't have the card view, so you can track things way more deeply. I haven't used it nearly as much, but like Trello, it has a wonderful modern user interface in a browser. It has the same sharing and is free to use for smaller projects.

It is great, at least for me, when you are down deep in writing code or a project like that because it has so many layers.

1. There is a big collection of chrome extensions for Asana as well. But I like the idea of Asana Global Task View so you can see all of your tasks.
2. Storypoint like Scrum for Trello let's you add points to tasks so you can estimate what things will take
3. Global View. See all your tasks aggregated across all Asana projects. Man, I would switch from Trello just for this.