Meenie50

Wow, this is fab!! Thanks! Some of that may be a bit above my pay grade right now, lol... but I'll learn it!! 
 

You could play around with using an elliptical gradient as the Fill for the text. For example, here's a basically orange title with an elliptical gradient running from purple to orange applied:

Here's the Fill dialog (from the Context menu) that I used to do that:

There are more complex ways to use gradients, so if that's what you want you might look at the tutorials, such as
 

Try nesting a couple of wiggly curves within the text. Give them a different colour, and perhaps a small gausian blur, maybe a bit of transparency.

File: Affinity My Title.afdesign

I guess it really depends on what your idea of "marbling" is.
I'd start with an image (or gradient or color splotches or anything with some variation) with roughly the palette you want (you can add in as you go).
Switch over to Liquify Persona and just let loose. You really don't even need any instruction. Just try all the tools. Can be as tame or crazy as you want.

 

There are so many ways you could achieve this using layers/masks/brushes and vector elements:
Personally, Using just the graduation tends to look a but flat...you could try adding some texture or creating some additional vector elements to be layered with the text:
Added a sample sheet with a number of options...I am sure there are many more...but that's part of the fun!
 
1.If you want to just stick to vector..try combining small irregular shaped elements into a group and apply subtle transparencies and colour graduations separately to each element (You could use the style panel to help you with this). Use Text as Mask Overlay (Mask to Below on layers panel)..so non destructive effect
2. Create a Pattern Brush using a tiled pattern and add to Base Texture of Brush. Again use Text as Mask Overlay (Layers)/or Select text element in Pixel Persona (Selection Mask)..and paint into shape
3. Same method as 2 but use a textured brush (combine a selection of nozzles) created from other images or found in resources!
4. Use a combination of graduated overlays (graduated rectangular elements)+Vector textures (Grouped random patterns created from multiple shapes) + Texture Brush in Pixel Persona
Hope this helps
 

See also for ease of work:
Using Text Styles Creating and managing text styles Character formatting (the related Character Panel) Paragraph formatting (the related Paragraph panel)

With the letter selected, adjust its baseline in the Positioning and Transform portion of the Character panel:

Use the text tool you've choosed to write the text and select with that the whole word, or just a certain letter of the text etc.
See also:
Working with text (in the online help)
Artistic Text
Frame text
...etc...
Official Affinity Photo (Desktop) Video Tutorials (200+)

Oh yeah, this is my kinda group!! Lolol!

Oh yeah, this is my kinda group!! Lolol!

I so agree, no silly questions! 
But I've been in other forums where newbie questions aren't so well received
I'm glad to see this isn't like them. We all have to be new at some point, lol. 
And humor I do enjoy as well 

I so agree, no silly questions! 
But I've been in other forums where newbie questions aren't so well received
I'm glad to see this isn't like them. We all have to be new at some point, lol. 
And humor I do enjoy as well 

I so agree, no silly questions! 
But I've been in other forums where newbie questions aren't so well received
I'm glad to see this isn't like them. We all have to be new at some point, lol. 
And humor I do enjoy as well 

There are three choices.
Black, Grey or Off (blacker) 

There aren’t any silly questions as far as I am concerned.   These beautiful Affinity apps do have a learning curve, and the most beautiful part (I think) is that the Affinity moderators and technical support staff are here to answer anything and everything with such helpful pointers.    Many other people with several  years experience also reply in these forums with helpful solutions.    So ask away in these forums if you need help!    I have learned so much this way!!