tompoland "try an immersion to see if the flavour improves" It means if you can't pull a good shot with it then stick it in a french press or sowden (or some other easy brew method) and see if it tastes good done that way. If it does it's roasted properly….
MWJB's comments around ratio and grind are important for newbies to understand. It's better to gain an understanding of these ideas when you start than it is to chase dogma and waste kilo after kilo of coffee never getting a good shot because you tell yourself you're doing the "right" thing e.g by dialling in the grinder to produce a 1:2 ratio in 25-30 seconds. The forums are full of people asking for advice because they've tried everything, different beans, different grind settings, new tampers, new grinders, and are at a loss, and then you find out they've always gone for a 1:2 in 30 seconds.
If you give people the idea that they should be aiming for a specific ratio in a specific time and they lack the understanding to make sense of what the implications are, the worst-case scenario they end up convincing themselves it's supposed to taste sour and strong because they're doing everything right, so it's supposed to be like that and it's just an acquired taste - and they never learn how to make good coffee - go to a handful of speciality coffee shops and you'll probably run into a few baristas who think that.
Unless you know the coffee, grinder, machine and water in use you can't recommend a dose, ratio or grind setting. You can certainly aim for something to start with, but it's far more useful and important that people know how to adjust the grind and ratio based on what they are achieving.
As a starting target, I'd say the goal is to achieve a good extraction, and the most likely ratio to achieve that in 25-30 seconds is not a 1:2 ratio for the vast majority of people out there, especially those with smaller flats or conical grinders and even more so if they are using light or medium roast coffee. If you must recommend a ratio a 1:3 (or more) is going to be much more forgiving. You can make adustments from there easily when you know how the coffee should taste and can be reasonably sure you aren't making two common mistakes 1) grinding too fine and 2) mistaking the possible bitterness of a low EY for over-extraction.
You could add another aside that judging an extraction based on how it looks from a bottomless portafilter is likely to leave yo chasing your tail because you think all extractions should look like the espresso porn on youtube. Sure, severe problems will be visible like completely uneven distribution or tamps and machines that aren't level, but other than that it can do more harm than good trying to "solve" 'patchy' extractions.