A smaller split sounds like it might be a good option for you— a Sweep, Corne or something similar. I’m biased towards Cornes— mine is a mini 5x3. I’ve found it to be really good for travel. Packs light, and works well on train journeys (table or back of the seat fold-down).

Also, I support that notion of experimenting with your own build. That’s exactly what got me where I am. Bought a prebuilt Lily58, then a full sized Corne, then wanted to make one myself and bought an Aurora kit. No soldering experience, and I found soldering the backlighting LEDs most difficult (I’ll be removing them sometime soon) but my board works and I’m extremely happy with it. :)

I’ve got a 5x3 Aurora Corne, plate case, large stand-offs so I can fit 1500mAh batteries under the board. Makes it a bit “high” profile, so to speak, but I’m okay with it.

Are you putting backlighting in your build? If so, that’ll be the biggest power drain. I built my board with backlighting, although I’ve never use it. Even so I get about a week out of the right side and a few days out of the left. Planning to pull the LEDs out at some point in favour of better battery life.

Depending on the case you pick you should be able to find one with enough space in the base for decent sized batteries. I was looking at some Scottokeebs cases at one point (https://www.etsy.com/uk/listing/1452267605/corne-keyboard-3x6-3d-printed-case-wired); one reason I didn’t go for in in the end was because the cutouts weren’t in the right places for the Aurora PCBs controls— mainly the power switch. Give some thought to what you actually need to access with respect to any case you get.

Apologies if any of this is obvious!

I’ve been happy with Memmy…

I'm on a 5col Corne. Love it. But my daily driver computing device is an iPad, and sometimes a MacBook, and I don't game on either. I have four layers, and I don't use function keys. I've got a bit of duplication between a couple of layers that I could probably refine, but it works for me. Having three keys for layers also works well for me.

Not all Corne kits offer the snap-off outer column these days, so be aware if you head down that road.

I think it's either money or time!

I took the middle road. Like you, I didn't want to / couldn't afford to spend huge amounts just to figure out what worked for me, so I spent A LOT of time in research mode. Subreddits, YouTube videos, Discord servers, the works. All to try to figure out what appealed to me. But I did end up spending more than I expected I would when I started.

The switch thing was a challenge. The keyboard switch testers I've tried haven't really done anything for me. I think maybe it's because I need enough of the same switches to actually mimic typing on to get a sense of how I might feel about a full board of those switches— just the one didn't really give me a full sense. Plus, there are a few other variables that come into play— keycaps, whether you've got any dampening/foam on your board etc. That's not to say you shouldn't get one. Something's better than nothing.

There are two things that really got me started on my interest in ergomech boards: a Vinpok Taptek (cool board but hella clicky for my tastes) and the Textblade (vapourware, but got me thinking about the smallest most practical keyboard I could get my hands on). So I knew I wanted something quiet, and I knew I was open to a less than usual layout/design. I think I may have even seen a split keyboard in the Textblade forums, I think it was an Ergodox or a Moonlander. From that, I ended up with my first board— a Lily58 with rotary encoders. Had someone build it for me, and I was happy... for a while. But the Lily58 isn't the most portable split, so I kept browsing.

Since then, I've picked up a wired Corne, an R2G Corne (relatively cheap, and easy to assemble), and a wireless Corne (had that prebuilt for me; no more TRRS or USB cables to worry about!). I could have stopped there, but I really wanted to know what it took to actually build a board from component level, so I bought an Aurora Corne kit and built a wireless 5x3 Corne. This one is the dream, and because I built it myself, it was cheaper than any of the other boards I bought prebuilt. Switches I love (Alpaca Silent Linears), keycaps I love (XVX profile, which I'd never heard of in spite of browsing a tonne of subreddits, ogling other people's keebs and asking what keycaps they were sporting), and eminently customisable (I just recently upgraded to 1500mAh batteries), all in a reasonably small, portable package. I reckon it's my endgame. It is. I still do browse on occasion, but I have no need to acquire/build another board. Not at all. Nope.

I mean, I did see an interesting Centromere Mini build the other day. But no. I'm sorted.

So, the takeaways:

• Figure out any preferences you might have, including any environmental considerations. Will you need to use your board in a quiet space? Will clicky switches get you murdered by loved ones or colleagues? I'm unlikely to go for low profile Chocs simply because there isn't (as far as I understand it) such a wide range of affordable silent low profile switches, which straightaway helps me to narrow down the kinds of builds I might be interested in.
• Prepare to do a lot of reading around (and YouTubing— there are lots of people on YouTube reviewing switches and things) about the various different components you might want for your ideal board. But remember, no matter how opinionated anyone else might be, your tastes are what matter.
• Find the cheapest way to test out a few staples (Cherry MX reds, for example?) and try to judge things relatively from there. Keycrox in the UK offers sample bags of switches for testing; I'm not sure about Europe based equivalents.
• I don't know whether you shop Amazon or not, but you can probably find switch testers there. You might also be able to test and return a few different boards via Amazon to help you zero in on what you might want.
• Maybe allow budget for a few different variants of cosmetic elements? Having experimented, I know I'm good with XVX, DSA and XDA keycaps. There are others I'm not nearly so comfortable with.
• Last thought: they don't happen that often outside the US, but you might benefit from heading to a keyboard meet-up if there's one near you within a reasonable stretch of time? https://kbd.news/meetups

Hope that helps!