Disclaimer, I am not nor have I ever been a professional in the plant industry. Take my advise with a gain of salt and apply what you can, leave what you can't. This is just my experience.
Have you looked at your calendar recently? (Do calendars still exist in a post 2020 world?) If not, you should know that our average last frost date is drawing closer! Here in Woodinville our average last frost date is Mid-April. While some will argue that we get frost until Mothers day, I use historical data from the WSU Weather Station located on the community garden property so I'm pretty confident in my "mid-April" date.
If you have a weather station nearby, use that data! WSU has a number of stations located all over the state including one that I see every time I go out to the garden.
That does not mean that I'm going to put my peppers and tomatoes outside on April 15th and expect them to be giving me fruit in a few weeks time. That DOES mean that I will be keeping a close eye on the weather starting in early April and looking for the long range forecast to have no lows expected that are below 40. I will still baby my plants for a few weeks and cover them with frost cloth if I'm unsure about the temps.
So what am I starting this week?
All my peppers. Peppers need warm weather to produce fruit, so I give them extra time inside and they will be planted outside in mid-may. This way I've got strong healthy plants that I will get fruit off of for a longer period of time.
Tomatoes. The average tomato should be started inside 8-10 weeks before your last frost date. (Tip: when you plant the tomato out in the garden, burry it up to the first set of leaves. The whole stem will grow more roots and you'll get a more robust plant!)
Flowers. I've already started some Delphinium's and Black Eyed Susan's which take a longer time to bloom. This week I'll be starting my sweet peas outside (yep, they will be planted directly this week, they like
the cold) and I'll also take a look at
my flower inventory for anything that needs 8+ weeks to get going.
Any cold season crops. Broccoli, kale, cabbage, peas, etc. All of my cold weather crops will be started now and transplanted out in a few weeks. If we get a big cold snap I will cover them with frost guard fabric. They are pretty hardy plants.
Here are some good resources on starting seeds if you need help. Seeds are a great way to cut costs while growing a wide variety of plants.