Ask HN: How do you handle performance monitoring at your tech startup?

I've purposefully made this question open ended, so feel free to answer however you see fit.

For some background, I'm a software engineer currently working with a seed-stage startup. We are developing a web app built on PHP Laravel, hosted in AWS Elastic Beanstalk, with a few dozen paying customers using it.

We've decided to invest in some performance monitoring, focusing specifically on page load times. We'd like to:

1) be able to measure and store page load stats from both the browser and server perspective.

2) set up alerts in case load times are getting worse over time or if they go over some threshold.

3) have some reasonable dashboard for displaying and drilling down into the data.

4) leave the door open to instrumenting/taking advantage of any other sensible monitoring/alerting needs moving forward.

It's been challenging for me to really gain any sense of what the best practices are right now for small-ish (less than 50 employees, seed/series A, etc...) tech startups. There seem to be a good amount of APM providers out there, but their pricing seems aggressive. There are a ton of other options. For example, I've considered setting up an ElasticSearch cluster and sending metrics over with some simple home-rolled middleware, and wedding that with New Relic Browser/Google Analytics/Simple Analytics/etc... in the browser.

So, how is everyone tackling this problem? I'm looking to start a conversation, hear some war-stories, and ideally learn about some setups that are working really well for your specific context/startup.