On race stuff, nothing! I hard wire everything. While that's not the easiest, it's the best.
The most popular connector out there is the Tamiya white connector. Honestly they are junk.
The best is probably WS Deans but they are a bit pricey. The connectors I like are Sermos/Power Poles/Lightspeed. They go by several names from several companies. They are the seperatable black and red connectors.
Your better off.
Don't skimp on an iron. get a good one that has replaceable tips. One good iron will last for MANY years. Mine is a Weller and I have had it for around 15 years and it probably has another 15 left on it.