In general, whenever you enter the ARM world, it must be fine.
I have worked with NXP Kinetis, Atmel SAMS70, ST STM32 and a long time ago with PI32. Now I'm starting with NXP i.MX RT1020 and RT1050, and although I'm still doing things with Kinetis, my idea is to migrate everything to the RT1020.
If you do not want to spend a lot of money, an ST Discovery evaluation board, with any STM32 is fine, and to learn, the book "STM32 Mastering" by Noviello.
The IDEs (for ARM) are usually based on Eclipse with some Plugin and configuration wizards, such as Cubemx for the STM32 and MCUXpresso + Config tools for the NXP.
If you want to directly start working with the really powerful, and not for that expensive, then the NXP MIMXRT1020-EVK evaluation board with an RT1020 microcontroller, LQFP100, Cortex M7 at 500Mhz is fine.
All the evaluation boards usually integrate the Programmer/Debuger (ST LinkV2, OpenSDA, etc...), but it is also convenient to buy a programmer, a Jlink EDU or a Chinese version, they are very good. I also have a Multilink PE, but this one is much more expensive.
I can not comment on the Cypress micros, I do not know them, nor do other manufacturers like Texas Instruments. Always look at the features, the price of the micro, the ease of obtaining it in traditional distributors (Mouser, Digikey, Arrow, Farnell, etc.) and that the evaluation boards and the programmer are cheap. It is also important that the development tools include the IDE and the C/C ++ compiler completely free, which is common in all ARMs, and a wizard to avoid wasting time configuring the periphery (Cubemx for the ST, Config Tools for the NXP, Harmony for the PIC32, etc ...).
I would not recommend the world of Arduino, nor the hardware available, nor its development environment that is quite bad and hidden things that it is important to know to move easily between microcontroller families and different manufacturers of microcontrollers, especially if they are ARM. The only thing that I found interesting about Arduino, and that other manufacturers would have to do, is to integrate a menu into the development environment with a lot of examples of source code for the most common applications, in this aspect it seems that NXP is improving in its recent versions of MCUXpresso, an environment that I like more and more.