I get lazy on Ammonia, Nitrite and Nitrate and just use a quick strip once in a while but know it's going to come back "clear" or at zero. If I get any "color" that would indicate more then 0 I'll then use a vial testing to verify the results.
I've got a couple of digital meters and I'll only go by a digital meter for PH. For the life of me I can't ever read the color correctly on stips for ALK or PH. The alk stip always has a "blueish" look on the strip while the color chart is "greenish". Thats just messed up. PH isn't as bad but there just isn't enough shades of red on the color strip in my oppinion to read it easily.
The only other "must have" digital meter IMHO is a salinity meter. I say "must have" if you do hypo. If you don't do hypo then your standard large floating hydrometer is normally "good enough". I've found the large floating hydro meters with the built in thermometer compensation work really well. They match up well with my digital meter while the swing arm style ones differ a little to much for my taste.
As far as test kits go for the basic PH, Ammonia, Nitrite & Nitrate tests just about any of the test kits work just fine. Save money and buy a cheap set of these. For things like Copper, Ca, Alk, Mg etc I'd only go with Salifert or if they don't have that brand go with another good kit maker like Sera.
I'm actually starting to pickup more of the Sera kits because they are a lot cheaper (for me) and they have compared across the board with results I get with salifert. If something doesn't look right I'll double check the results with a salifert test kit.
I typically will buy "the best" right off the bat and then "a good" kit when I'm about half way through the first kit. I'll then switch to using the "cheaper" kit because I know I've got the old standby on hand if I need it. I also like to double check each manufactures results with another. I figure my fish/corals are worth it.
Carlo