This code, when put under dotspacemacs/user-config, enables math preview mode.

latex-math-preview.el

  ;; --------------- begin latex preview configuration ----------------- ;;
  ;; latex and auxtex layers needed
  ;; activate using the vim-like binding `[space] , p b`

  ;; automatically inserts newline at the end of long lines
  (add-hook 'text-mode-hook 'turn-on-auto-fill)

  (setq TeX-auto-save t)
  (setq TeX-parse-self t)
  (setq TeX-save-query nil)
 
  (load "auctex.el" nil t t)
  (load "preview-latex.el" nil t t)
  (require 'flymake)
  (defun flymake-get-tex-args (file-name)
    (list "pdflatex"
          (list "-file-line-error" "-draftmode" "-interaction=nonstopmode" file-name)))
  (add-hook 'LaTeX-mode-hook 'flymake-mode)

 ;; enables preview of pictures
  (eval-after-load "preview"
    '(add-to-list 'preview-default-preamble "\\PreviewEnvironment{tikzpicture}" t)
  )
  ;; --------------- end latex preview configuration ----------------- ;;