Tips for fighting light pollution (needed)

I live in a Bortle 5 area and my exposures are typically 30 secs for Luminance (i.e. no filters), 90 seconds for Red, Green or Blue filters and between 180 secs and 300 secs for Narrowband.  If anything your exposures should be less than mine given your location.

So, with 10 minutes exposure you are maybe spending 9 minutes of that capturing light pollution.

Filters will help a lot.

The technical answer is covered here https://youtu.be/3RH93UvP358

you need to balance sky (shot) noise and read noise with exposure duration and gain.  Not fun, but it does come down to the statistics of the noise.
I suggest, design some controlled experiments trying a few ideas and compare the results of stacking ~15 images per whatever conditions you choose.  Prove to yourself what works

It seems like a few hundred dollars for a filter after what you have spent is nothing compared to getting bad results with what you have.
I live in Bortle 8, I would not spend the time and effort without a filter. 
You have a nice mount and camera, the filter is a very small investment to get good images compared to the money you already spent.

You will probably still use short exposure times, as that's enough to swamp read noise with your camera in your light polluted skies. Camera noise really is not your problem. Shot noise and gradients are. To fight the shot noise of light pollution, you need to shoot a lot of subs. For the brightest targets shoot 10h, for most galaxies, 20h, for nebulae 40h: Most emission nebulae are as faint as reflection nebulae without a narrowband filter. At Bortle 5, I need about half these times, but more is always better. Then cull the subs, mercilessly, especially those with high clouds. They will introduce complex gradients and artefacts because they throw off normalization and pixel rejection with subs swamped with shot noise. 

As you won't want to calibrate 15s subs of a 40h project, you need to be able to shoot longer subs without burning out more stars: Use the lowest gain that your camera can do. I have a QHY268M and in Bortle 5 I can do 120s Lum subs without overexposing on a F/3.3 Epsilon due to the "extended well depth" mode. For the hypercam, set "LGC" mode and gain to 0. You should be able to get at least 60s subs that way, maybe 90s or even 120s.

Optimize your telescope: Use a long dew shield. Get rid of any reflections, blacken the tube, possible mirror surfaces and interior surfaces of any adapters. Use something like Black 2.0/3.0, but educate yourself on its use before, it's not straightforward. Alternatively, velour also works, but not as well. If it's a mirrored telescope, get information on baffling and see if any can be added/optimised without vignetting your chip. Any light not from your target that lands on the chip is a problem - and there is a lot of that around you.

Optimize your surroundings: Try to get to a shielded place away from stray lighting. Turn off your own outside lights (and ask neighbours to do the same, if possible). Get your community to employ measurements against light pollution (many of those actually save money in a rather short timeframe).

You could also do mobile imaging: If you can get to Bortle 3, you will only need 1/4th the exposure time and fight far fewer gradients. Now that I write that, I think I should get my … up and do more mobile imaging myself. It's just so convenient to have the scope sitting in the backyard…

Also, don't despair, and have realistic expectations: You're trying to make images of targets that your pixels only detect one photon of every few seconds. And that with a sky that is bright enough to read under.

Hi Andy,

Looks like you've been given some good tips without having to spend any money which is what you asked for.
Everyone's budget is personal and so I fully understand why you can't spend anymore right now. Just carry on the way you are, every nights session is an opportunity to focus on what you have, make the next incremental improvement and bullet proof all those little things that want to go wrong in the dark.
When you can afford it, then get yourself a couple of filters. It doesn't have to be really expensive as you may think. There is A 1.25 IDAS LP2 filter on Astrobuysell.com (UK) for £55 at the moment for example.

Whilst your waiting for the money, use those endless cloudy night here the UK researching what you need and looking for bargains

Check out https://astronomy.tools/calculators/ccd_filter_size tocalculate what size filter you will need and research how you will fit it in your imaging train.

I also shoot with an OSC (ASI533MC) and 1.25 filters close to the sensor saved me alot of money.

If it helps, from my experience, I would get one light pollution filter for reflection nebula and galaxies which I would only shoot if the moon was not up.

One narrow band filter for emission nebula. This will blow you away when first see the results, it's the single biggest step change in my progression. As said before here, you can shoot with this in a full moon, but you will probably get halo's around bright stars and not suitable for gathering OIII. It won't bother you to start with, but you will soon want better.

I also use an IR/UV block to reduce star bloat but that's because I'm in bortle4 (sorry to gloat and don't often use my light pollution filter.

Hope I'm not teaching you to suck eggs, but wanted to share some of my findings in case it helps. If you're guiding 10mins then you've got yourself in a great position to get some images you will be really happy with

Steve