If the result you got for the cover was what you wanted then I have no complaints at all. It's your magazine and I'm not in the position of being able to say anything is wrong.
magazinedesigning.com is a good place to look for articles and inspiration. It's well written and has interesting things to say that anyone looking at making their own magazine should have a look at it. Sometimes the advice can be conflicting but that's just the nature of something as diverse as publishing.
I totally agree with the quote about not restricting yourself to rigid layouts. I've lost count of the number of times I've read a newsletter (or similar) and seen the last three or four words of a paragraph orphaned off to an otherwise blank column just because the designer didn't bother, for instance, changing the column widths. A tiny tweak of a column width can put things right without the reader even noticing there's something different.
As for the use of different layouts then, again, if that's what you wanted then it's not for me to say otherwise.
If you'd allow me to give some specific advice I'd like to offer some minor changes that I think might help with future issues (I'll concentrate on the page 7/8 article):
1. Look for words that are by themselves and try and put them back together with their "parent" sentence. For instance, at the bottom of the first column on page 7 there's the word "On" all alone when it should be with the "October 23..." sentence. Try using a non-breaking space to keep the words together. ("Chupa-chupas" on page 8 is another example, but the other way round.)
2. Look for single lines of text and try and put them back together with their "parent" paragraph. For instance, the line at the bottom of page 7 column 2 "Over a period..." would look much better if it was with the rest of the paragraph on page 8. Try using a column/frame break to fix this.
3. Try and keep the top and bottom of image frames aligned with the corresponding top and bottoms of the text. That doesn't quite sound right but it's difficult to explain. By way of an example, look at the bottom-left image on page 7. The top-right corner of the image goes across a paragraph break and looks a bit awkward. If the top of the image was moved down a bit so that it matched the top of the "F" in "From" it would look neater. There's no golden rule on this so try different things and see what looks best. Maybe moving the image (or both images) up the page so it's more vertically centered would make a big difference?
4. Try and make sure that the padding around image frames - ones where the image fills the frame - is uniform on all sides. For example on page 7 there's a bigger gap between the image and the text above the image than there is at the right-hand side. Uniform padding normally looks nicer.
5. Try and make the gaps between columns a little bigger. At the moment you've got it at around the same width as a capital "M" but it would look better being at least two "M"s. This goes for the inside margin also (the text on the two pages is too close).
If you've tried to do all of this you might find that the text doesn't fit onto the pages anymore. In that case you can try slightly tweaking the font size, baseline grid, or using hyphenation to get it to fit.
Then, if there's still stuff wrong, you can look at editing the text slightly and see if some small changes make a big difference. Also, try using manual line breaks to see if you can get it looking better, automatic line breaks are not always in the best place.
All in all, good page design comes down to getting the overall look right and then a whole lot of minor tweaks to make it all look really good.
My second-best bit of advice would be to keep practising. Professional magazines look that good because the people working on them have had years - or even decades - of experience, and you can't get that overnight.
And (I think) my best bit of advice is to keep having fun experimenting with the software and see what you can make. If you're enjoying using it then you're likely to uncover more features which will come in useful.
I'm looking forward to seeing the next issue.