Yeah, I think (as I've experienced myself) that you should stick to one thing, especially in the beginning. Here it's best to choose something you're already familiar with. Meaning Algo-Trading if you're already able to program, longer term investing if you have experience in Accounting and Management of bigger companies, etc. Interestingly I noticed two things as I progressed.

Firstly you'll understand how others (who haven't choosen your path) trade. At some point I realized, how many long-term profitable discretionary Traders trade and why it works. But as this isn't my path it's just a fun thing to know, that you can maybe exploit later on.

Secondly, especially in the later stages (when you really know what you're doing) it seems to me, that it is actually better to look in other directions. Those directions don't have to do something with trading directly, as long as you can somehow project your learnings onto trading. There are dozens of examples of this in the trading world like Ehlers applying Digital Signal Processing and FM/AM Processing onto Prices to catch cycles.

Good knowledge in other fields will probably help you to get more profitable, but only if you've already advanced sufficiently in your path. And you should never leave your path and always come back to apply what you've learned to your path.

But that's just my experience and everyone's approach to trading is (and should be) different.


To the question above:
When I'm building strategies I'm following a plan, that seems to work quite well for me. (As I've noticed it is quite similar to JCL's Plan, definitely check it out). Meaning that I'll search for Filters (one to two at max) to apply to my signal. Sometimes I use ones I already found/developed, sometimes I develope/search for new ones. Since every strategy you trade should be different not every filter will fit every strategy. I'm not struggling with finding a particular filter but sometimes it is just a bit difficult to find ones that are fitting.

But in my experience you get better at finding them with time (just as with signals) and if you don't find a fitting one, that may mean that you're idea is just not working. Document the idea and move on.