In our view prebiotics are more important than probiotics, because without the right food source, your probiotics will just be passing through and not doing anything. You need to feed the right microbes inside your gut, and hopefully most of them are there already. We did not use probiotics in our clinical studies and we got significant results with SeaFibre alone.
That said, you do need to "update" and diversify your microbiome profile through your diet regularly, and this is why it is good to eat fermented foods, including cheeses, fermented drinks or yoghurts, sauerkraut or kimchi etc. This is the best source of probiotics.
However if you don't eat fermented foods or have been taking antibiotics, then probiotic supplements can be useful, but they are not very diverse.