Right now, it is still hard to get fitness equipment. Either it is back ordered or it is really expensive used.
You might be able to come across a deal for 300 lbs of weight (255 plates + 45 bar).
With only these things, you can improve your fitness.
A squat rack is great for safety and for other things, but you can adapt exercises to hit a lot without it.
Barbell weight lifting exercises without a squat rack
Deadlift - The most basic exercises. Lift the weight off the ground. As with everything, have generally good form. Does not have to be absolutely perfect (because body types and goals), but you should be generally good because that indicates safety. You do not want to get injured.
Floor press - Basically bench press, but on the ground. You will not be able to do a lot of weight at first if you just started lifting. Be very careful. I wanted to get a squat rack specifically for this exercise. The other exercises I felt fine without. Bench press is probably the most dangerous exercise to do by yourself.
Zercher squat - Look it up. I like the version where you deadlift to your knees, then wrap your arms in between your legs. Use a set of fat grips or something to protect your arms.
Barbell row - deadlift the weight and row. Bent over straight back rows are okay too, they target a lower part of your back. Pendelay off the ground are really nice because they get you to move mass.
If I had to choose one exerise, it would be deadlift.
It target so many muscle groups that are functional as well.
Minimal exercises
Deadlift
Pull ups - mount a bar to a wall or a door frame
Running
Minimal lifting exercises with a rack.
If I had to choose the most basic exercises for a well-rounded program, these would be them.
Deadlift
Squat
Bench press
Barbell rows
If you want to add something, put in pull-ups.
If you want to make it more complicated, add in core workouts (so many to choose from) and do them in between the sets.
Workout alternatives
Stuff gets boing, plus, you should actually be working variations of these movements to be healthy.
Deadlift - straight legged deadlift, hip thrusters
Squat - zercher squat, lunge. Bulgarian split squats - some people love them, I haven't ever gotten into it
Bench press - 45 degree incline press, overhead press, z-press
Barbell rows - flat back rows (these hit your lower back too), pendelay rows, deadlift rows...these are all really similar
Good mornings
Be cautious about overworking areas. For example, if you do heavy deadlifts, maybe do more upright barbell rows instead of straight back rows. Maybe go lighter on good mornings.
If you want to add something, put in pull-ups.
If you want to make it more complicated, add in core workouts (so many to choose from) and do them in between the sets.
For me, weights are difficult to get a crazy sweat and hype in. I do not like pushing that hard or fast with weights. Easier to do like sprints and jumps and running to get that cardiovascular system engaged. HIIT type workouts.