Seáinín’s advice is good. I can suggest a couple of other things. One is to watch episodes of dramatic TV such as Ros na Rún. I find this to be more challenging than listening to podcasts, which tend to be relatively easy to understand (for me), as there seems to be more attention to annunciation than is usually contained in everyday speech. Ros na Rún is an abundant source of what I would say is very close if not identical to the way people actually talk in the Gaeltacht (from my limited experience being there), which is to say they talk like most native speakers of a language do: quickly and often indistinctly. There are other shows out there, especially if you want another dialect (Ros na Rún is fairly heavy on the Conamara Irish, although there are speakers from other regions). The show CU Burn is great for Ulster Irish. You can find bits of both these shows on Youtube (a lot of full episodes), and you can watch plenty of full episodes of Ros na Rún on the tg4 website.
An exercise that is worth doing, when you understand what you’re hearing is to repeat everything you hear as you hear it, trying to keep up with the flow of the dialog. This might be hard (unless you’re quite good). This really helps with the raw muscle memory and fluency of your actual mouth. The second exercise which helps with your memory and your actual interpretive skills is to listen to a short section of dialog and then pause it and try to repeat as much as you can from memory. This is probably going to be a good deal harder, even though it might sound relatively easy. If you can do both of these things without effort, you’re probably quite good.
Another thing to do is to work on translating stuff from English to Irish. I find this quite a bit harder than translating from Irish to English. Translating everyday speech (things you hear people say in real life, things you want to say) is usually a bit easier in terms of vocabulary but usually highlights where you might be lacking in knowledge of word usage, subtle things, and idioms. Translating more official things like news stories will usually turn up a bunch of gaps in vocabulary for things you may not ordinarily talk about anyways but are probably good to know.