My 2 Cents on learning something basic skills that will be crucial to later work: DO not skimp too much on quality, unless you are really money-restricted or are willing to spend overproportionally time on something.
Reason: When you learn something new and have to get some practice at it, all variations should be reduced to one - the one you are currently working to improve.
Means in your case: Use the same soldering iron, same boards, same solder so that your skills alone are the only thing you will vary to get some experience.
This means also that the abovementioned stuff has to come in consistent quality to NOT introduce some variations to the things you do.
And when you use very low quality stuff to work with, you will spend lots of (unnecessary) time to figure out what is going wrong or at least sub-par.
So your question to go for decent, not overly expensive tools is legit, but given the overall costs of a spool of decent quality solder that will last until the soldering skills are solid, there is not much to save.
Just looked at amazon US, and I understand the question: On a search for "solder wire" lots of chinese "fantasy" brands with random names came up, not much brands that I would recognize as well-known.
One sprung to me:
Weller WSW SnPb (T0051403099) Solder Wire, Dia: 1.0 mm / 0.039 in, Wt: 100 g / 3.527 oz, Alloy Sn60Pb40, Flux content 2.2%
These 100g should last a while, at least it should be very sufficient to get your skills trained so that you are capable of getting some feel for your iron, reheating time, behaviour of solder when tinning bigger areas etc.
For US residents, that are not affected by regulations regarding lead-free solder, this is probably a very good point to begin with- the classic 60/40 solder mixture with flux included in the wire.
Also the 1mm diameter makes it melt quickly, but produces enough amounts of solder to get THT stuff done easily- and with the length of wire you have to feed to the soldering iron you get a good feel how much stuff to use.