I will kick this off.
I needed a cheap or free system to keep my records.
Purpose of records:
1. Know where I stand financially (current value of holdings, regularly revalued)
[also holdings reconciled to share registries, FX$ balances reconciled)
2. Help inform purchase/sale decisions, ie. "management information"
3. Tax records

I trade NZX and ASX, so multi currency.
About 50-100 trades per year, maybe 10-20 holdings at any one time (and will go on for decades into the future, I hope). BTW, this is investing (not trading) for tax purposes.

I looked at simple accounting systems, but none could handle all of the above.
I now have one spreadsheet file (split into several worksheets) that does it all. It has grown more and more complex over it's 2 year life, with many small improvements and a couple of times completely rebuilding it.
I tried to rebuild as a database once (as I think the structure of sharetrading and holding logically better suits a database) but it got too tangled, and have stuck with the spreadsheet.
I am just about to rebuild it again as have found selling AUD shares and then using the proceeds to buy (staying in AUD), applying FIFO to exchange rates, a bit clunky.
Also can't decide if I keep sold investments in the main records worksheet or hive them off out of sight to reduce clutter.

There are worksheets for:
transactions; AUD bank a/c; summary position/valuation;
Also : company research; summarrised company research; notes from tipsheets & forums; and portfolio strategy

This is what I do. What do others do?
This will be a horses for courses thing. The bigger your activity the more you can afford proprietary recording systems, and the more you need it. And don't get me started on Charting systems.
(I used to be an accountant but that's all rusty since last did that 15 years ago, but gave me some spreadsheet skills).

ToBo