Here is my advice, for what it is worth, based on my personal and ongoing experience of learning Welsh.

I shall start by stating the obvious: learning a language is hard. Further, whereas I recall learning of research not so long ago that indicated, somewhat counterintuitively, that the ability of adults to learn a language was not significantly different from that of children it WILL FEEL HARDER, for a variety of reasons but including all those other commitments adults are fitting this activity round rather than being in school, being taught in the language they are learning. I recall a nasty statistic of a few years back that less than 5% of adult learners who start a Welsh course will become 'fluent'. There certainly seems to be a remarkable drop out rate in the first few years.

Go Immersive and Intense (if you can)

Kids (in Welsh schools) benefit from the 'immersive learning experience'. My main suggestion would be to replicate this as far as is possible as an adult, for example by undertaking an intensive course. Further, I would suggest that this is particularly important near the start of your studies. I did one 2hr lesson a week for the first 6 years of study and while my local provider offers a more accelerated option nowadays with some supplemental online study, one lesson a week doesn't really cut it, even if you are also attending regular 'informal learning activities'. I switched to 2 classes a week for year 7 and, while it was bit of a struggle initially with other commitments, I have seen the benefit. In retrospect I wish I had done a month of intensive summer course Welsh at the very beginning to gain initial momentum, effectively completing 2 years of part-time study in 4 weeks. It would also have meant that I wouldn't have been playing catch up with my kids (so much) for the last 7 years!

Support and Practice

Having a fluent (and willing) partner/ friend/ mentor/ colleague/ spouse/ offspring even you can practice with will make a big difference if you are not 'going intensive'. Speaking Welsh with someone who is fluent at best daily but at least weekly will speed your learning no end. If you don't have someone suitable ask your tutor/ local Welsh for Adults coordinator if they can assist. Or there is ffrinDiaith. Alternatively or additionally make use of the excellent value informal learning activities that your local Welsh for Adults Centre offers, if they are anything like mine in Cardiff anyway.

Other Resources and Tools

Also consider using supplementary resources such as

Pob lwc!