What kind of bags are you looking for?
If your looking for panniers the best in the industry is Ortlieb but they are expensive; the next best becomes more subjective, but for the money I think the Axiom Monsoon 45 is very difficult to beat, maybe match but not beat. The Axiom Monsoon is designed like a dry bag so it's waterproof unless you submerge it! No matter if you get the best Ortlieb you still should put things that you don't want to get wet into ziplock bags, and line the pannier with a plastic trash bag so anything that you're carrying that has liquid won't spill and stain the inside of the bag.
Handlebar bags it's tough to beat a Topeak Tourguide DX, it's large and roomy, however not waterproof so you need to spray this bag with a couple of coats of water repellant spray like Kiwi Camp Dry Heavy Duty Water Repellant, and respray every season. The Topeak does come with a rain cover but I don't think it's all that good either so you should spray the cover as well. Yeah I know spraying both seems like an overkill but you are talking about rain, and heavy rain can get into things you thought wasn't possible. Also like I said about panniers, if you have something in the bag you don't want to get wet ziplock bags to the rescue.
Seat bag, again I like the Topeak Aero Wedge, these come in I think two different sizes and can expand, again they too will need spraying. There is another cheaper alternative on Amazon for just $12 called the BV Bicycle Strap-On Bike Saddle Bag/Seat Bag/Cycling Bag; I bought one because over 2,000 people have given it 4 1/2 stars and what I found is that it's made of the exact same material as the Topeak! I haven't had it long enough to see if it will last as long as the Topeak but it should and if it does I won't over twice as much to buy the Topeak anymore; I also sprayed this bag too.
Toptube bags, a lot of the bags I looked at used very thin material which didn't inspire confidence for durability, but the two that I saw that did inspire confidence was again a Topeak brand simply called the Fuel Tank; Timbuk2 Goody Box which is a tad too small for me but it looks well made; and the Specialized Burra Burra Top Tube Pack; I ended up with the Specialized because it was a tad larger than the Topeak, both said they held .75L but the Specialized was a bit larger? Someone was wrong in their size measurement. But all the three that I mentioned did have waterproof liners inside, the Timbuk2 used a lid to keep water out, but the other two used a waterproof zipper; I did not spray the Specialized because the outside material is waterproof as is the liner, my phone has a waterproof cover on it so no need for a ziplock bag on it.