Ezdis

I'm fairly new to cycling having only just started in June 2021. My current bike is the Priority Gotham Edition in a size small. I feel like I went with too small of a frame as I'm 5'8" with a 29" inseam. I feel like I could use more gears as 3 often doesn't feel like enough.

I've been looking at the Marin Kentfield either the 1 or 2, can't decide if I would need the 3 extra gears or not. The Poseidon Flatbar X is also tempting since I could save some money while getting a 10 speed wether I need the 3 extra gears or not, but I'm worried about it being "too aggressive" of a riding style for me.

Using competitivecyclist dot com
Inseam 29 in
Torso 24 in
Upper Arm 13 in
Lower Arm 13 in
Upper Leg 15 in
Lower Leg 21 in
Sternal Notch 56 in
Total Height 68 in

I might have gotten some of the measurements slightly off, but I did the best I could. I currently ride 12-15 miles a day for exercise and commuting, I plan to slap fenders and a rear rack on whichever bike I get and might swap from a flatbar to a slightly curved bar, maybe even a jones bar not sure just yet.

Iride01 

Why do you think it's too small? If you can extend the saddle to the proper height for you and still have enough of the original seat post in the seat tube then it's probably okay. If you are wanting to sit more upright then you might just consider some riser flat bars if a stem can't get you higher.

A bike with more gears on the rear might still leave you no better climbing gears. Assuming the same front chain rings an 8 speed 11-34 rear will give you the same low climbing gear as a 12 speed 11-34 rear. Depending on what brand and model your DR is you might can just swap cassettes and chain or change the front crankset (chainset).

Ezdis

I have the stem as high as it can safely go and it still feels too low for how high I had to raise the seat and there's quite a lot of stand over room.

The Kentfield I mentioned is a 11-34 for the 7 speed, the 10 speed is a 11-51, and the Poseidon is a 11-48. I'm just not sure if I really need the extra gears on the 10 speeds as I'm not sure how to compare the low gears to the low gear on my current bike.

Iride01 

The bars are too low?

I'm thinking you got the wrong bike then. You need to look for something with more frame stack. And possibly not a road bike. Which is actually a misnomer term IMO as road bikes aren't the only bike made for the road. What we call road bikes are for fast endurance type riding typically 3 or more hours, though many of us never put that much time in for a single ride.

You might look at cruiser style bikes which will have a higher stack with bars higher than the saddle.

Carbonfiberboy 

To compare gearing, we use a measure called gear-inches. https://en.wikipedia.org/wiki/Gear_inches
You divide the number of teeth on a chainring by the number of teeth on a rear cog, and multiply by the wheel diameter. For convenience, we don't use the actual measured wheel diameter. For road bikes we use 27" and for MTB we use 26". The wheel size is shown on the tire, though for technical reasons, modern road bike wheels are now called "700c" though we still use 27" in the calculation. The smaller the number, the lower the gear. Gear-inches in the 20's are quite low.

Carbonfiberboy 

The big difference between the 2 Kentfield bikes is the size of the largest rear cog. If your area is fairly flat with minor hills, the "1" would be fine. If it's hilly, the "2" would be more practical. The number of gears is a much smaller consideration. The bike with more gears really needs them to make the differences in gear-inches between the gears smaller. The two bikes will then have similar differences between gears. It's just that the "2" gearing goes lower with those extra 3 gears.

For bikes of this type, bar height even with saddle is regarded as low normal. Bars a few inches above the saddle is fine, too. Getting the bars too high becomes a problem if there are steep hills.