What to get for my second saddle?
Product req questions are now Off Topic.

So you need to figure out what you want from your new saddle.

Start by measuring the width of your existing saddle, right where your sit-bones make contact.  Then use the cardboard or rice-sack method to measure your physical anatomy.    This will give you a number in millimetres.

Then look at the general shape of your old saddle - is it pointy?  Do the sides flare out late or early?  You either want a saddle that matches the overall shape, or tweaks any area that you feel could be better.

A new saddle is a chance for you to try a slotted design in the middle, should you suffer from numbness.

Finally the padding and covering are important too - your old saddle will probably not be worn out given it was a rail that broke.  So squish it with your thumb and try to gauge the thickness.   The covering is 90% likely to be some kind of vinyl or plastic.  If you like it, duplicate that.  If you don't like it, consider what else is available.



Now you say your bike only cost you $50 of your currency.  There's an implicit "...so I don't want to spend much money on it" and I disagree with that.

The saddle is one of the three contact points between you and the bike, with the pedals/feet and bars/hands being the others.   I'd have no problem buying some good shoes or pedals or bar grips for a bike. 

Saddles are generally more difficult because they are quite hard to trial.  Some cities in the world have saddle libraries where you can hire a saddle for a month for a small fee, ride it, and then swap it for another one.

Leather saddles are even harder to trial, because they conform to the rider over time.  So they're somewhat like 10 pin bowling shoes.

Remember, any part can be removed from the bike and used elsewhere, so a nice saddle can be swapped onward if you break the bike.

Also ask around some other cycling coworkers, or check your city for a bike cooperative.  I have a number of spare saddles that I'll never use, which have turned up from bike teardowns or clearance sales.