Hello lr1022,
The cost of oil is one of the problems that hobbyists have all wrestled with and I spent hours searching the web for small amounts at reasonable prices but regrettably I found a remarkable similarity in pricing from all suppliers of Moebius oils for instance.
If you are just practising, a cheap working watch is a worthwhile purchase, strip and clean it then use a cheap generic watch oil when putting it back together. It is hardly worth spending much on oil for a cheap Chinese movement for instance, however, you will still gain the learning experience.
If you trawl old postings in the forum you will find good reasons to spend more on oil for treasured watches. I used to try to restrict my interest to just a couple of makes - Accutron and Tissot and only bought the oils for them but over time I weakened and started looking at other movements. You will find guidance on the forum for the subject. Mark has covered the topic for instance and we have an oil specialist who gave quite a detailed post on oil generally. Just put in a search.
In conclusion, if the watch you work on is expensive or treasured you probably should use good oil and that I'm afraid comes at a premium.
Cheers and welcome,
Vich