Using the resource as provided by @pnuts, I have found the following answers to my questions.
A detailed schedule of the train can be found here. For example for the morning commute, these are my likely leave- and arrival-times:
There is a lot of valuable and clear information available here. What it boiled down for me is the T-Jove card. As explained by the official website:
A personalised travel card valid for an unlimited number of journeys in 90 consecutive days from the first validation for under 25s providing proof of age by means of a valid national ID document, foreigner ID document (NIE) or passport. The number of the ID document must be printed on the travel card.
With points of sale at
- TMB bus and metro automatic vending machines
- TMB customer service and information centres (Punt TMB)
- Other Integrated Fare System operators (stations)
- Other operators' information centres
After reading through the options what each means, consider using the Ticket Calculator though when I used it it seemed rather broken (according to the calculator, most of the trips I'd take would be around €50/trip).
Very important/useful is the pricetable which gives you an idea of how often, for how long and how far you can go with each ticket.
In order to accurately find out how many zones you're using, you can use below image:
Mataró is in zone 3E so I have to account for 3 zones: 1, 2 and 3. Using the above table then tells me the T-Jove card is best (3 months, unlimited trips and 3 zones for €210).
This will differ based on your age, your length of stay, your nationality, your disabilities, etc.
Also an important note:
Which means of public transportation can I use with the tickets?
During a given time, a ticket can be used for the following forms of public transportation, if changing is necessary. The same ticket may be used again, without the machine "chopper" marking a new journey:
- Train (Renfe).
- Catalan railway train (FGC).
- Cable car (Funicular of Montjuïc) in Parallel stop, line 2, the color purple line.