Aquarium salt is a good preventative for velvet disease, which betta fry get very easily. I use it all the time. Any water conditioner is fine but I use Stress Coat and have never had a problem with it.
Yes you need to use the water conditioner. ALL fish need water conditioner. Let's go over the basics of spawn costs:
10 gallon tank, $10
25-50 watt heater, $25
Plastic plants, $6
corner or spinge filter, $10
air pump and valve, $20
50-100 jars, $50-$100
San-Francisco Bay Shrimpery, $20
Brine shrimp eggs (for above), $7
Microworm culture, $3.50
Aquarium salt, $6
Methylene Blue, $5
Two one-gallon jars for your breeding pair, $6
20+gallon tank (heater and filter), $100
And finally, a breeding pair. Do you want to breed good, nice quality fish or petstore mutts? With hard work you can fix mutt bettas but high quality fish are a much better choice. It's up to you. The price range for a petstore is $7-$10 for a pair and from a breeder is $20-$60.
The end price: $328. If you buy a good quality pair: $398. at least.