ChainSet, Cassette advise

I run a compact 50/34 chainring then got a 12-28 cassette.having a triple you should be able to climb walls with even a 25 on the back.if it is a long climb always try and start at a good tempo and keep 2 left in the block as long as u can in case u struggle

Your gearing should be adequate to climb most hills, though you could fit a larger cassette (I always find it reassuring to have another lower gear, even if I rarely use it). I think the issue is probably technique. Everyone is different, but this works for me.
At the bottom of the climb, don't attack. Find a gear in which you can ride comfortably, similar cadence to that on the flat. Then drop one gear, keeping the same cadence. Then ride up, keeping in the saddle, remembering to turn the pedals rather than stomp on them. Then when you get near the top you can put in an extra effort and go past the riders who passed you at the bottom.

You've got a triple, I'd not bother buying a wider range cassette really.
If you're struggling with a triple, no matter what you buy you'll struggle.
You need to train to get better, just eat well and ride, taking in climbs more (you don't get better avoiding them).
When you say drop into the lowest gear which one do you mean?
You might be under gearing yourself too much as well.

If you have a triple then your rear mech should take a pretty big cassette. Saying that, I am fat and unfit and I get up pretty much everything (eventually) on a 34/27 lowest gear - which is higher than 30/25.

Do not be tempted into climbing as fast as possible. Learn to find your pace and an effort that you can sustain for the duration of the climb. Once you've done that then you can start to push slightly harder than this and improve.

Oh, and ignore the pace others go up hills. It's not helpful to try to chase down 9 stone whippets, just demoralising. Find your own pace.

You could look at whether you can fit a larger cassette; this is limited by your rear derailleur but most current ones will cope with 28 teeth, some 30 or even 32 teeth.

More importantly, you need to get to better at riding hills. Losing weight can help but to get better at it you have to do it. Lots. There are thousands of articles in magazines and on the internet about how to climb hills but you should just eat healthily and ride your bike.

Some people will tell you to spend money on upgrades but that won't help you get up hills. If anyone says that the weight of your bike is holding you back they are lying.