I have a lot more domains than you, and getting it under control has been a huge challenge.
I use Excel .. with multiple sheets.
Basically I have a different "sheet" for the raw inventory download from each registrar.
Another sheet for my Estibot data download.
I also have a master static page and a non-static page.
The static sheet is where I put in hard information like purchase price, purchase date, etc
The main master sheet pretty much pulls everything together and gives me calculated columns, as well as pulling all the important data from everywhere else. It's where I put my pricing.
I also have a sheet at the end for stats, like I can tell you at a glance that my portfolio is 94% .com.
It's actually a complex monster .. and probably the biggest reason why I've been a VERY bad domainer and not having all my domains listed everywhere or even priced. Frankly, it's a miracle I'm a profitable domainer.
I'm actually back on track and have been working on it this weekend .. it hasn't been up to date in way over a year at least. Can't wait until I'm done. It's a true masterpiece! lol .. But don't let it get too out of date .. then it's a nightmare!
The great thing about using excel, is that when you are organised, you can create cool formulas like multiple listings and such, giving lots of helpful relevant data.
That being said .. if you only have 50 domains, then it's not as important .. but if you do see yourself growing your portfolio in the future .. 100% get a system in place now .. otherwise it'll become a nightmare.
Take a look at my daily lists at NameCult and here at NamePros .. that's mostly Excel .. still a LOT of work .. but the styling/formating automation lets me spend more time actually manually going through names with my eyeballs ... that's one thing I'd never automate .. I find so many great domains by eye that others all miss because they use tools!
Good luck with it .. Excel is my 2nd best friend (after little Steamie) .. but also my worst enemy! lol