A simple tip: measure and record everything you do. Swims, bikes, runs. Distances, times, pace, heart rate, power if you've got it. Keep split times in your watch while you're training, and transfer them to your training diary when you get back. If you don't have an online training diary, I highly recommend Trainingpeaks - the free account there is exceptionally well designed and useful, the premium account even more so. I've just switched to using it with my athletes and they all love it.
The more information you collect, the more you can analyse, the faster you're going to get.
Sounds too simple? 90% of the improvements you're going to see in your performance are going to come about because of belief. Your mind is the most important part of your training. Even if you've got a decent training plan, and most importantly, you're completing the training sessions - I still believe that the most important element of your performance is belief in yourself. Perhaps the biggest benefit of training session is mental rather that physcial - it helps us believe we are capable of more than we thought we could do. Our minds are like small children - they need constant reassurance that they're doing well, and that they're getting better!
The most cost effective investment you can make is a good waterproof stopwatch with a lap function, one that has the option to record multiple laps. I recommend my athletes buy one of these - Timex Ironman stopwatches. If you hunt around they're available for about £20 online. If you can afford heart rate and GPS on top of that, then great - but if not, that £20 stopwatch will be the best investment you can make. (Note - I'm not affiliated with Timex, but have used their watches for 25 years and think they're great. I've never used the company in the link - please exercise due dilligence when buying online...)
Take responsibility for your own timing. At the pool, at the running track - take lap splits, and write them down in your diary when you get back. Look back regularly over your training diary and find improvements. Go to the pool or the track knowing what splits you should be seeing - and make sure you hit those times. Find comparable swim sessions, and watch how you're getting a couple of seconds faster on your 100m repeats. Unless you're paying for 1-2-1 coaching, it's unlikely that any coach at a group session will be able to keep lap splits for you - and you need that information to build your belief that you're getting faster.
Here's a thought I'm going to leave you with this week - what if 'seeing improvements' was the key to getting faster?
See it and you'll believe it...