Gothic alphabet NOT fraktur

with xelatex:

\documentclass{article}
\usepackage{fontspec}
\setmainfont{Segoe UI Symbol}
\begin{document}

I have some actual Gothic (as in the alphabet used by the Visigoths
and Ostrogoths) that I want to include in my .tex file (e.g.,
"").

\end{document}

This is more a complement to David’s answer than a separate answer, but the question about my comment needs more space for clarification than a comment allows.

Here’s a small example, extracted and simplified from the Junicode manual:

% compile with lualatex or xelatex
\documentclass[12pt,a5paper]{book}
\usepackage{fontspec,microtype}
\setmainfont{Junicode}[
  Contextuals=Alternate,
  Numbers=OldStyle,
  SmallCapsFeatures={LetterSpace=7}]
\AtBeginDocument{\setlength{\parindent}{1em}}
\begin{document}
ss19 produces Gothic letters automatically from transliterated text,
while ss20 produces Latin letters from Gothic. Example:
{\addfontfeatures{StylisticSet=19}jabai auk ƕas gasaiƕiþ þuk þana
  habandan kunþi in galiuge stada anakumbjandan, niu miþwissei is
  siukis wisandins timrjada du galiugagudam gasaliþ matjan?}

You can also enter Gothic text directly, without using a stylistic
set. Example: 

Since the Gothic alphabet has no distinction between upper- and
lower-case, capitals and lower-case letters are transliterated the
same way.
\end{document}

Depending on when you last updated your TeX Live, you may need to use the older fontspec syntax:

\setmainfont[Contextuals=Alternate,Numbers=OldStyle,SmallCapsFeatures={LetterSpace=7}]{Junicode}

If you don’t want to use Junicode throughout your document, you can do something like this:

% compile with lualatex or xelatex
\documentclass[12pt,a5paper]{book}
\usepackage{fontspec,microtype}
\defaultfontfeatures{Numbers=OldStyle}
\setmainfont{TeX Gyre Pagella}
\newfontfamily\goth{Junicode}[
  Contextuals=Alternate,
  StylisticSet=19,
  Scale=MatchLowercase]
\AtBeginDocument{\setlength{\parindent}{1em}}
\begin{document}
Plain English, in TeX Gyre Pagella, followed by {\goth jabai auk ƕas
  gasaiƕiþ þuk þana habandan kunþi in galiuge stada anakumbjandan, niu
  miþwissei is siukis wisandins timrjada du galiugagudam gasaliþ
  matjan}, supplied by Junicode.
\end{document}